Identify this possible parasite?

Saw this on my cats tail last December. When I tried to remove it with a tissue, she became agitated and ran off. When I checked her later it was gone. Trying to figure out what it was. Looked to me like a worm, about an inch long, but it wasn't moving. Checked with my local vet at the time I saw it and they did a fecal test that came back negative for worms. Showed them the photo and they just said it "wasn't something they usually see". She had to be euthanized today because of an idiopathic chylothorax and I'm just wondering if this is a parasite that could have triggered the condition. I know it's a long shot, but I'm just curious.

Hello!   This looks as though it might be a nematode of some kind (that could be construed as cheating, by the way:  a nematode is simply a roundworm, but it sounds impressive, doesn't it?)  Nematodes tend to be round in cross section and flick around, if that seems to fit.  However if you need to know the species etc then capture it in a small pot and show it to your vet, who may ID it or send it away.  If appropriate, they might also recommend an appropriate worming programme - or change the existing one - to prevent recurrence.