Not sure why people are jumping down this guy's throat and saying that it didn't happen? He doesn't have an argument, he is asking us a question.
I have a planted tank with many shrimp in it, when a fish dies I usually never find a full body, just a skeleton that looks something like the one you found. The pleco died for one reason or another, and then was eaten by fish/snails etc. If you have a large population of Malaysian trumpet snails or the like, I wouldn't be surprised if they cleaned a fish carcass in a night.