At first, the déjà vuvuzela appears to be a common musical instrument of no worth whatsoever, other than the few gold coins gained from selling it. However, should the hero attempt to play it, he will get the odd feeling that he has done so before. This feeling is unnerving to most heroes, who only remember killing monsters and drinking beer most of the time - so the hero is almost always more eager to sell this particular artifact.
The déjà vuvuzela was created by a young blacksmith in Last Resort. His girlfriend had a horrifically spotty memory, to the point where she would only take two steps away from her house before forgetting where she was planning on going. With the help of a budding scientist (who happened to be a good friend of his), he tried to create something that would help his girlfriend remember things more often, but almost all of his attempts ended in failure. That was when the young man turned to music. He had heard many stories of music being used to unearth memories. These "stories" had yet to be discovered in any written documents, and he particularly enjoyed making instruments rather than the usual weaponry. Excited, he began the project straightaway.
Over the next few months, the blacksmith toiled day and night, searching for a sound that reverberated with a slight echo, and thus sounded familiar to anyone who heard it. The young man's girlfriend received the instrument a few days later, and she was overjoyed to have a memory that she could recall at any time, even something so small as playing an instrument. She spread the word about the joy she had gotten from her present, and everyone wanted one soon enough. It earned a deal on SharkTank, and the rest (as they say) is history. Hopefully your hero will remember where the coins came from, but it is doubtful - at least until they sell the next one.