That happened to a little hamster I got from Petco. I got this beautiful cream colored little Syrian. She was really active when I first brought her home. We only live 15 min from the pet store. I put her in her home. She was running around exploring, eating, drinking acting like all was well. Then over night she was just quiet, sleeping in her little nest ball. Would only come out to pee. She stunk terrible. I called the store and told them what she was doing and also about the odor. They told me she probably had "Wet Tail" and that I could either bring her back and they would sell her to someone else OR that I could feed her some cabbage and wash her bottom with a warm washcloth. They never said anything about them taking her to the vet. I immediately read online about "Wet Tail" and called a vet. They had me bring her right in. Then I told the vet everything she was/wasn't doing, the odor and what the store told me to do. He could not believe it. He checked her out, heart, lungs and told me that she was terribly dehydrated and was having respritory problems already. I only had her 1 1/2 days. He said there was nothing that could be done basically as she was already too far gone and she was sick when I got her because they don't get into this condition over night. The store said they would take her back, give her medicine and pay for the vet bill. Then, they called the next day and told me she died. I felt very bad. That was my little Su-Mee.