I definitely regret not going back the next day to check but I think I did what I could, which was just telling the employee, who sounded concerned and it looked like she was going to go over to the hamsters as I left.
I'm not sure the shop did anything
really wrong in this case except not keep a close enough eye on animals that grow up to become very territorial and solitary. (In all fairness this might be hard to achieve some days as the animals are on the one half/corner of the store and usually when I go in they have about 2-3 employees on the floor with one having to stay at the till all the time. But they should still try to keep a close eye on the animals).
On a more uplifting note: I went to the same pets at home today and adored over the animals. There was a group of 4 young roborovskis in a pile sleeping together! They looked like they each were about 3cm big (they did look old enough to be sold though). One woke up and gave a massive yawn and then drifted back off, curled next to it's sibling
I wanted to cry they were so cute!