I stay on the 6th floor and the next closest plant is 50 metres away. I have no idea how a plant that's been soaked so many times in the last 3 months have a tiny snail on it. =) Good thing i plucked it out.
If this was a recent acquisition it could have been a hitch-hiker.You may need to use something specifically for snails. I believe we call them bush snails. Good luck.