What does a decomposed fish look like?

I have some rescue fish so I only had 4, noticed one of my black neon tetras vanished from my tank. I've read they can jump and this did happen to be the most energetic fish in the tank but I'm missing like 5 gallons out of a 30 gallon tank so it would have had to jump really high.

I did find something that almost looked like a ball of fibers stuck in a cheaper plastic "tree" I bought from walmart though and I'm worried that the fish could have gotten trapped between the pointy plastic "leaves". It was very very fibrous and white, I'm curious if this was my fish.

Should I possibly remove the cheaper plastic tree thing?