There are no signs or proofs that a person has attained moksha after death to the ordinary person. Similarly, there is no sign or proof that a living man has attained moksha. In his Pancadasi, Sri Vidyaranya Swami says (VI. 287-288):
Enlightened men may differ in their behavior because of the nature of their fructifying Karma. This should not make the learned think otherwise about the truth of knowledge resulting in liberation.
Let the enlightened people behave in any way according to their fructifying Karma, but their knowledge is the same and their liberation is the same.
and in his commentary on the first verse, verse 287, Swami Swahananda says:
There is no uniform rule about how a knower will behave. A well-known verse says: 'Krishna lived a life of enjoyment, Suka renounced even before Vedic initiation, vast empires were ruled by Rama and Janaka and Vasistha was a great ritualist, but all of them had the same illumination.'
And in the Introduction to Swami Swahananda's translation of the Pancadasi, T.M.P. Mahadevan says:
The final court of appeal is experience,--the plenary experience, which is the fruit of inquiry. In fact, the texts of scripture are but indicators of that experience. Thus, in Vedanta, the nature of Truth is sought to be expounded on the triple basis of scripture [hearing], reasoning [reflecting], and experience [meditating] (srutyuktyanubhutibhyah, V, 56, & XI, 89).