Worm in Poop

Question
Last night, I decided to throughly check my almost 10 week old Holland Lop's droppings because he had been having pretty soft cecotropes earlier in the evening.  I saw a milky colored thin line one a few of the droppings.  I thought it could just be a hair or something, but when I poked it, it moved.  It's really thin, cylindrical, a bit jelly like, and about .5 to 1 cm long.  I took his stool samples to the vet this morning and they did a fecal exam, which turned up negative for parasite eggs.  The exotic pet vet wasn't there to take a look at him herself.  The lab tech didn't notice the worm thing I saw and had explained to them.  Do you have any idea what it could be?  Is it something that I should be worried about?

Answer
It moved on its own or it moved like it slid a little? If it moved on its own, it would be some sort of parasite. If it did not, it could be mucoid enteritis. This is somewhat common in young rabbits, and it can be very dangerous for them. Are there any other signs of anything wrong? Does the belly look a little bloated? It could also be something as benign as a little bit of something undigested. If there are no more, it is likely nothing, but if he has another feces problem or irregularity of any kind, it would be good for the exotics vet to look him over carefully.