More than likely that is the breathing tube. Mine sometimes have theirs out while under water for long periods of times. It contracts and twists and does change shape somewhat. It may have been damaged causing it to hang out more. If the snail is eating and not wasting away then it should be fine. Snails do develop parasites and are often a host to parasite larvae that then go on to infect fish or other animals. Most captive breed ones are not usually infested because of the closed systems they are raised in. You could try to get a closer look at it by holding the snail and waiting for it to come out of its' shell. Mine would sometimes cruise around on my hand but some will not come out while you are holding them.