Short answer: it depends. But it was a "gift" so you don't have any legal "right" to it. So it depends on whether it is easily located and whether those handling the estate see the painting as trash or treasure.
Three obvious cases:
Case 1: The casual friend had a will, and the painting is specifically bequested to someone other than you. Then you are SOL, unless that person is willing to give/sell it to you.
Case 2: No bequest mentions this painting, but your aunt is a famous artist, the picture is significant $. Then you should offer to buy it back.
Case 3: Your aunt is an unknown painter, the painting's value is mostly sentimental, and no one else alive has a sentimental attachment to it. Then whoever is handling the estate will be glad to unload one more item.