It depends on what ink was used, how it was cured, and type of nylon. When I worked at the shop, we had a gun that shot sort of a dry cleaning adhesive solvent thru it to clean up small mistakes. I did use it on some large area stuff, but can't recall if I ever did a nylon bag. Probably depends a lot if it's a coarse weave or smooth as well. Screen printing on stuff is kind of a cross between alchemy and a shell game.
You might look for a local screeen printer and ask if they have a spot-cleaning gun and what they would charge to shoot the image out. At best it will peel off with no problems, at worst it will do nothing, with a possiblity of washing out some of the nylon color, or leaving a ghost image.