Do my hamsters miss each other?

I will admit right away that I am a hamster novice, and I was going on the advise of the pet store, that it was ok to keep my teddy bear hamsters together. They were kept together at the store, so we put them in a cage together when we brought them home. They always snuggled together, shared food, water, toys, and slept together. But today, I caught them fighting so bad, that I could actually hear one of them screaming. We separated them immediately, but now they seem lost without each other. I feel bad and don't want them to miss the other, but I don't want them to kill each other, either! Can they get sick from separation anxiety? I don't want them to get sick, or to be sad or upset.