The glitter from the gift shop, the glitter from the people in the sauna, and glitter from a snow globe I just acquired are all the same type of glitter. So the glitter others woke up with was likely from the snowglobes.

This, however, does not explain why there was glitter in the gift shop. The snowglobes are impossible to open by hand, unless one happened to be leaking. You would have to break them otherwise. But there was no glass in the gift shop.