They certainly do! Have a look at this (video of x-ray showing hamster stuffing pouches from BBC programme).
https://www.youtube.com/watch?v=6X8In96zV9Q
The video that follows it is good too! Same TV series "Ninja Hamster" and the "Toilet Paper thief" one is really good. By the way the hamster ball theory in the Ninja Hamster video is debatable. Most hamsters wouldn't stop at the top of the stairs and would roll down which is dangerous, so don't think anyone should rely on a Hamster sensing how far down the stairs go!