Another reason not to discard fishing line

For a couple of days, I'd been hearing a slight squealing noise when applying the brakes on my car, so I took it to the shop thinking it was time for a brake job.   The mechanic fixed the squeal: he removed some fishing line wrapped around the brake line.  How that managed to make the brakes squeal puzzles me, but I was happy not to lay out a couple of hundred bucks.  I just hope it wasn't some line I left on the garage floor!