[souffle]

I'm so sorry for your loss.
Like every little creature there must have been something going on inside that just gave out. It can happen in any species and often we just never know what caused an early passing.
Over a year is actually middle aged for a hamster. You gave him the best and he sounds to have had a lovely life with you.
Even if you had seen a vet it is really unlikely they would have been able to do anything as a robo has a very tiny system and any little problem has a huge impact on them.
You did everything you could considering his behaviour and he passed secure in his own bed warm and well loved. Run free at the bridge Bruce