More photos in the comments. Is it supposed to be connected to the motherboard? I found it in the case. It wasn't connected. I think that the backside is some sort of thermal patch. I can tell that it's not a camera but I'm very confused and the connection reminds me of more of a laptop or phone connection not something you would see in a PC. The data matrix contains the same text as the white sticker.
Unfortunately whatever it is, it is indeed broken off, which makes it harder to identify. The numbers on the flex don't lead to any hits.
It's not a connector, too shallow for pins to seat anything. I doubt it's a speaker. My guess is some kind of sensor, but for what is hard to tell.
It's possible that whatever this is fell into the PC from some other equipment, and isn't related to it. Likely something portable, as desktop PCs don't use that type of connector on the other end
I declare you the likely winner. After looking all over inside of the computer, I couldn't find anything that seems like it's broken or missing a part. I suspect that it really did just fall into the case at some point.