I have quite a number of stories where my work has been stolen, as well as copyright infringement. Which one to tell??? Where do I start? I do not know! The first one was by a gallery. Ten years later, the gallery owner looked me up and brought it back to me (damaged, of course).
The second one was also a gallery. Never got that one back.
The third was a coffee house.
Then a few people who never paid.
I had a band file a copyright on my painting for their album cover (out of spite, really), when they had no right to do this. It was my original painting, created previously (not a work-for-hire) and it was used as the cover, like a license. I never allowed them any part of a copyright, but they filed one on it anyway.
I've had a couple artists paint/copy my original paintings and put them up for sale on their websites, then ask me if that was okay. Ha ha ha. One never asked. I contacted them and they just took them down for sale but kept them up for show and accredited that they were "after" me. After a couple years, their site no longer existed at all. Maybe she stopped painting, I don't know. She was a beginner, and it was flattering, but it still wasn't too cool.
I've had Artist's book stolen either out of a gallery or misplaced by another gallery. No one knows for sure, but it was not paid for. I was not compensated for it. Same gallery sold a different artist's book to a museum and never collected from the doner because of some misunderstanding with him. Who ate it? Me.
I've had work totally destroyed by two different galleries, one in Miami, and one in Nashville. The Nashville gallery destroyed two and one was fixable. The other was totaled. The Maimi one destroyed the other by shipping it back in a flimsy box. It had glass on it. The glass broke and cut through the paper and linen backing.
Those are the ones I can think of for now.