Hello WaspishJupiter and welcome to Hamster Central. I wish it was under better circumstances, but you came to the right place. First, your little guy was so beautiful. I love the expression on his face in the photo. Thank you for sharing it.
Now...it is not only possible for a hammy to pass away the way yours did, but it happens more often than you know. I lost my beautiful Ted E. Bear in the very same way you did. One very important thing you need to know; when a hamster starts going downhill like that, going into such a deep sleep, they are preparing to let go of life and move on to the Rainbow Bridge. They withdraw into themselves and get on with the business. They aren't all that aware of what is going on around them. So, no. He didn't suffer, he, most likely was slipping in and out of coma.
Ted E. Bear was just fine, doing his hamstery thing, when he suddenly stopped eating and was staggering around and sleeping the way you describe. Same with his eyes. I still, after over 50 years of having gerbils and hamsters, have not decided which is better, a fast short downward slide, or the longer deterioration before the end. Truth to tell, for the hammy, I guess the fast way is best.
From what you describe, you did what you could to ease him. I doubt a vet could have done a whole lot more. Grieve for him, but don't ever blame yourself. You gave him a very good life and, for him, that was what mattered. {hugs} for you. Play well at the Bridge beautiful boy.
