Fish tank...weird help please?

First off, it sounds like you have too many fish in your tank. You should only have about 10 SMALL fish in a 10 gallon tank. But anyway, sometimes if a fish dies, it will be quickly eaten by the other fish and snails, so unless you spotted the dead fish right away, it may have been eaten. Check behind and around the tank to make sure no fish jumped out. That sounds weird, but it has happened before.