These things happen.

A friend of mine went to a garage sale on Australia and bougt a load of fishing tackli in tackle boxes.

One of them had a paper bag full of uncut gemstones the deceased had hidden there.

He got the stones cut, made a good deal of money.

On the other hand a 'friend' of the family came to see my mother's books when she was clearing out my dad's study to make space. He was a book dealer. Told her nothing was of any value but he'd give her 25 for a few he quite liked.

Took and original, signed German copy of Mein Kampf by Adolf Hitler. It turned up in auction a couple of months later with a low estimate of 125,000. Some friend.