I have a snail in my fresh water frog tank but can't tell if it is alive and/or sick?

My kids received one of those self-contained fresh water African Dwarf Frog tanks. The tank included 2 frogs, a bamboo, a snail, and some pebbles. After doing some research online we found out that the habitat provided by the retailer wasn’t the optimal for the frogs so we decided to get a larger tank. Before we transferred the frogs to their new tank, we noticed that the snail was at the bottom of the tank instead of stuck to the sides of the tank. We have transferred the frogs and the bamboo to a larger tank, but have not transferred the snail because we think it might be sick. How do we know if it is OK and if it is safe to transfer it to the new, larger enclosure?