We know that he is not omniscient in the sense of knowing everything simultaneously, only that he has access to all knowledge when he wants it, at least according to Hariharananda Baba. So how is he then omnipresent; how does he know he is omnipresent if he only perceives something from one location? And what about the jivanmukta? Is he omnipresent as well?
Kena Upanisahd` 1.5-8 say, on OMNIPRESENCE of Brahman, as follows:
What speech cannot reveal, but what reveals speech—know thou That alone as Brahman, and not this (anything objective)that people worship here
What mind does not comprehend, but what comprehends the mind— know thou That alone as Brahman, and not this that people worship here
What hearing fails to hear, but what hears hearing— know thou That alone as Brahman, and not this that people worship here
What smell does not reveal, but what reveals smell— know thou That alone as Brahman, and not this that people worship here
Mundaka upanishad 3.2.9 says as follows:
स यो ह वै तत् परमं ब्रह्म वेद ब्रह्मैव भवति नास्याब्रह्मवित्कुले भवति । तरति शोकं तरति पाप्मानं गुहाग्रन्थिभ्यो विमुक्तोऽमृतो भवति ॥ ९ ॥
sa yo ha vai tat paramaṃ brahma veda brahmaiva bhavati nāsyābrahmavitkule bhavati | tarati śokaṃ tarati pāpmānaṃ guhāgranthibhyo vimukto'mṛto bhavati || 9 ||
He who knows that highest Brahman becomes even Brahman; and in his line, none who knows not the Brahman will be born. He crosses grief and virtue and vice and being freed from the knot of the heart, becomes immortal.
Coming to the aspects of Guru and Jivanmukta, we have to understand that a Jivanmukta is the one, who got SELF REALISATION or REALISED the BRAHMAN, while living in the present body.
Hence, as per Mundaka upanishad 3.2.9 - He who knows that highest Brahman becomes even Brahman, a Jivanmukta is a BRAHMAN, and thus he is OMNIPRESENT.
Sage Vāmadeva Gautama is one such Jivanmukta.
And, a Jivanmukta may be a Guru or may not be a Guru, depending upon the prArabdha of the body that Jivanmukta is in.
Some Jivanmuktas may complete their life time, without being noticed by anyone as such or without guiding any disciples.