Firstly, Can anyone really Curse Lord Shiva?
Do the sages who come for fractions of time in the Universe have power to curse the Lord Shiva? No, it isn't possible. When in a story we see that someone curses Shiva and Shiva suffers from it, it is not that Shiva suffers because of effect of that curse, it's because Shiva wishes to do so. Tapa Shakti of Rishis are of no comparison to curse Lord Shiva who has infinite powers. For eg. When Lord Shiva and Lord Vishnu went to Daruvana taking the form of man and women then sages curse Lord Shiva there, but he is totally unaffected by the curse:
अतिवपरुषं वाक्यं प्रोचुर्द्देवं कपर्द्दिनम् ।
शेपुश्च विविधैर्वाक्यैर्मायया तस्य मोहिताः ।।
तपांसि तेषां सर्वेषां प्रत्याहन्यन्त शंकरे ।
यथादित्यप्रतीकाशे तारका नभसि स्थिताः ।।
तं भत्स्यं तपसा विप्राः समेत्य वृषभध्वजम् ।
को भवानिति देवेशं पृच्छन्ति स्म विमोहिता ।। [Kurma Purana II.38]
Then the sages spoke extremely harsh words to Siva, having the matted locks of hair over the head and under the influence of Maya, they started pronouncing curses on Shiva. But all the words spoken by the sages as well as the curses, became infructuous before lord Siva, in the same as the stars disappear on the rising of the sun. Thus finding their tapas being of no consequence, the confused sages, went close to the bull-bannered Siva and asked him, “Who are you Sir?"
So, curse on Shiva only works when he wishes it work. Thus all curses which Shiva will receive are already pre-planned and those curses also act to serve as something good.
Secondly, it isn't necessary that how powerful a sage maybe he is all aware of Shiva-Tatwam. For eg. In the Daksha Yajna episode many sages and Gods were deluded by Maya of Uma and they forgot that it is impossible to perform a Yajna without invocation of Parameswara. Only Dadhichi was the sage there who had known that it is impossible to perform Yajna without invocation of Lord Isha. Sage Bhrigu was also there and he too was deluded. When Sati died he even created Army of Ribhus to fight against Shiva Ganas and he was latter punished by Virabhadra and Manibhadra:
He (Virabhadra) strucked and smashed Bhrigu while the valorous Manibhadra kicked him on his chest and plucked of his moustaches. [Shiva Purana Rudra Samhita chapter 37]
So, being deluded by Maya sages and even gods can forget things like invocation of Parameswara. So, it isn't surprising that Bhrigu gave a similar curse which was not actually a curse at all. So the thing like Shiva being worshipped in Linga form from time beginning can be forgotten by sages too in the influence of Maya.
Thirdly, entire Universe is just play of Shiva. He takes everyform which exists here and plays with himself. Svetasvatara Upanishad says 'Sarvãnana Shirogriva' / 'All necks his necks, all heads his heads... ' and Vedas also say 'Sarvo vai Rudrastasmai Rudrãya namo aastu' / 'Rudra is everything that exists, Salutations to him who is such.' And the SataRudriya of Yajurveda also talks of Lord Shiva being in the form of each and every form of Universe. Some verses I also discuss in my answer here. So, the sages like Bhrigu are none other than Shiva. In the Mahabharata also in the Anushashana Parva it is stated:
He assumes the forms of tigers and lions and deer, of wolves and bears and birds, of owls and of jackals as well. He it is that assumes the forms of swans and crows
and peacocks, of chameleons and lizards and storks. He it is that assumes the forms of cranes and vultures and Chakravakas. Verily, he it is that assumes the forms of Chasas and of mountains also. O son, it is Mahadeva that assumes the forms of kine and elephants and horses and camels and asses. He assumes also the forms of goats and leopards and diverse other varieties of animals. It is Bhava who assumes the forms of diverse kinds of birds of beautiful plumage. It is Mahadeva who bears the forms of persons with sticks and those with umbrellas and those with calabashes among Brahmanas. He sometimes becomes six-faced and sometimes becomes multifaced. He sometimes assumes forms having three eyes and forms having many heads. And he sometimes assumes forms having many millions of legs and forms having innumerable stomachs and faces and forms endued with innumerable arms and innumerable sides. He sometimes appears surrounded by innumerable spirits and ghosts. He it is that assumes the forms of Rishis and Gandharvas, and of Siddhas and Charanas. He sometimes assumes a
form that is rendered white with the ashes he smears on it and is adorned with a half-moon on the forehead. Adored with diverse hymns uttered with diverse kinds of voice and worshipped with diverse Mantras fraught with encomiums, he, that is sometimes called Sarva, is the Destroyer of all creatures in the universe, and it is upon him, again, that all creatures rest as on their common foundation. Mahadeva is the soul of all creatures. He pervades all things. He is the speaker of all discourses (on duties and rituals). He resides everywhere and should be known as dwelling in the hearts of all creatures in the universe. He knows the desire cherished by every one of his worshippers. He becomes acquainted with the object in which one pays him adorations. Do thou then, if it pleases thee, seek the protection of the chief of the deities. He sometimes rejoices, and sometimes yields to wrath, and sometimes utters the syllable Hum with a very loud noise.
So, Shiva himself reducing his consciousness is in the form of sages like Bhrigu also. So, curse of Bhrigu is like Shiva playing with himself. But whatever Shiva does it always results in good as also discussed here:
Since by all his acts he performs sacrifices for all and seeks the good of every creature, therefore he is called Shiva. [Anushasana Parva clxi]
The episode of Bhrigu cursing Shiva happened near beginning of present Kali-Yuga which is also continued with Lakshmi being angry and Vishnu coming in the form of Venkateshwara. In the Kali-Yuga the path of Vedas is distorted and people have low intellect. So, worship through Shiva-Linga can be the best method to worship Shiva. Through Shiva Linga one can worship without knowing mantras too, ie. by offering water only too. And in this sinful age of Kali worship through Linga has immense merits. So, we can say that curse of Bhrigu is just plan of Shiva to reinforce his worship through Linga.
