When do you expect to see the vet?
(Also, you want to make sure that this isn't a vet that will require you to turn them over to them, allowing them to decide whether it lives or dies.) Every state is different and, it seems, every vet is different.
Yeah, squirrels definitely do not like the sound of quickly moving water.
Also, the experienced members of this forum have likely far more familiar with squirrel health issues than most vets, some of whom can be close minded and intolerant of anyone who questions their assessment. (but it sounds like it isn't that sort of vet, but just putting out the potential issues in advance.)