Even in the best covered tanks, a Nerite Snail escaping from an aquarium can be a pretty common occurrence. Once an aquarium hobbyist introduces snails into a tank, the never ending battle of keeping the snails in the tank begins.
A Nerite Snail spends a great deal of its time in the water near the lower portion of the tank. But then they park themselves just on, or slightly above, the water-line. A Nerite Snail seems to be comfortable staying dormant there for long periods of time. Nerite Snails don’t seem to dry out there and they somehow stay moist.
Its important to take periodic shell counts to make sure all snails are present. Check on the outside of the glass and in power filters as well. A Nerite Snail may be hiding in the filter while eating edible material like algae off the hard plastic surfaces.