DM Dallas said:
I have never 'uploaded' anything. It just gets added when i drag tokens onto maps and such.
Anything you drag from your computer onto the map area is uploaded to your art library.
All browsers cache image data for faster rendering of a page you visit more than once. Typically, older images in the cache are rotated out as time goes on. An image that was deleted from your library could still display for some time after the original was deleted. This is nothing special about Roll20, just the way browsers handle images.
Without access to your account, the rest of us can only hazard guesses as to what might be going on. You need to file a Help Center Request and get a ticket for dev attention. You can point them to this thread in your report.