What are some examples of lost media being found at stores?

2 other unreleased Activision Atari 2600 games were found this way: One was called Hard Head while the other one(a tile puzzle game) remains unidentified. It's unknown who programmed either of them; the 1st looks to be an official Activision title considering a PAL proto was also found years later alongside being well up to Activision's standards at the time, meanwhile no other copy of the tile puzzle game has been found & the game itself isn't really up to their standards, which could imply that it was presumably made by a fan of the company & was sent to them to see if they would accept it.