I bought what i thought were mystery snails. I had a tank w no heater. My snails were active n happy. I put a heater in and one died n the other looks close to it. I took the other snail out n put it in cold water n it was fine again. The pet store ssid to re introduce it to the heat w a plastic bag. Sid that ...,snail doesn't like it. Taking her no out n putting her in cold water where she's happy. Is this normal or do I not have a mystery snail.