It all depends on what species it is. Seeing as we don't have a picture of it (you said it was too small), and the fact that it would seem that it arrived via hitchhiking its way on one of your plants, I would assume it might be one of the 'pest' variety. As long as there isn't too much excess food, its population should be minimal due to lack of said food as well as algae that it could also feed on.
Should you start to notice more and more snails, then you could start to take action. I've heard of assassin snails (never owned them, as my 10 gal only has plants right now and nothing else), as well as various loaches and such that love to eat snails. Copper-based medication designed for killing snails might work, but could easily foul up your tank if their populations are high.
Can you provide some more details on your tank, such as size, occupants, etc...?