I have no first Han experience with this & DrK's advice is very good. I also remembered seeing this video this week from Erin's Hamsters explaining about torpor (the hibernation like state hamsters can go into to) & how she has dealt with it in the past. Like she says, this isn't the definitive right answer just how she coped with it. Also explains about difference between a hamster in torpor & one that has past away.
http://youtu.be/o66s2INAAGI
Hope this helps you.