The nature of ancestral property will extinguish once there was a partition done and each individual has been allotted with their respective shares. From your contents it appears that the property belonged to your grandfather and subseuently partitioned and your father got his due share out if it. If that is so, then it is not at all ancestral property and the share of property in your father's hands will be his own and absolute property hence he was entitled to marketable title and on that basis the gift deed executed by him to his brother can be held legally valid, of course if it was done on his own and free volition. You have a chance to retrieve if you can prove that it was obtained under force and coercion by the uncle.