Ringworm is quite common in cats, especially kittens. I guess the vet must have missed it or mayb it contracted the fungus in between the time from the check up to the time collected. No one is really to blame here but I think the manager went a little too far with the passing of the fungus from your daughter to the kitten or vice versa and the health and hygiene of his store etc... The staff there are usually quite understanding and humble but I've not met the manager, so I'm not to judge.

Was the manager actually the manager or the guys that are mainly working there?

hmm... I haven't met the manager there before :/