Hello. I live in Italy and...

Question
Hello. I live in Italy and I bought what is called a Dwarf Hamster or a Russian
hamster here a couple of weeks ago.  It was a young hamster.   It was quite
active and ran around its wheel a lot.  It ate and drank normally and appeared
to be very healthy.  I noticed that the last couple of days it seemed to be
extremely active (almost hyperactive) and it started biting a lot when I held it.  
Yesterday I put a clean glass jar with the top off on its side in the cage with a
little of its bedding inside because I thought the hamster would enjoy going
in and out of it.  In fact it started sleeping in there. I don't know if this had
anything to do with the hamster's death but is the only change that we made
to the hamster's environment recently.  Today it was normally active and then
this evening we noticed all of a sudden that it was dead in its cage.  I have
heard that hamsters can have heart attacks - could this be what happened
especially since it had been so much more active in the last couple of days?  
And why would its behavior have changed in the last 2 days?  Could it be that
it was frustrated because it had a small cage?  It was a good new cage - solid
bottom, open wire sides and top that he climbed around on and I plan to get
another hamster and I don't want to have to buy another cage if it is not
really necessary.  I can't tell what we did wrong with this hamster.

Answer
i don't think you did anything wrong at all.sometimes if you are new to keeping hamsters it can seem a little daunting and you wonder if you're doing the right things. however i think the way you started with yours was fine.to be honest i just think it was just a coinsidence that it died so suddenly as it doesn't sound like your little hammy was sick.
what was in the glass jar before you cleaned it? if it was food then that is fine. if it was a cleaning product then small particles could have remained in the jar when you put it in your hamster's home. also, was the temperature inside the jar too warm at all?
to be honest, if your hamster chose to put its bed in the jar then it must have been quite comfortable and i don't see that it could have been the cause of death.i think you were just unlucky in this case and shouldn't worry too much about getting another hamster.
i'm sure the cage you have already will be fine for your new hamster, just make sure you clean it and any toys thoroughly with disinfectant first.
its worth pointing out that when you get a new hamster they can sometimes be a little stressed by the move as there are lots of different smells and sounds in its new home. it is wise to leave your new hamster in its cage alone for a couple of days so it can get used to its new surroundings first.as long as its got enough food and water it'll be fine.
good luck with your new hammy...i'm sure you'll be a great parent.
thanks for your question, jewel