Your poor Geno! I'm glad you took him to the vet right away and that he had meds.
Max's first corneal ulcer came from an accident while I was bathing him. I had a handful of conditioner and he turned quickly and the conditioner got in his eye.
All of the rinsing didn't prevent injury. Anyway, his eyes recovered with no permanent damage.
A groomer should know about products used on the head, although this product said "tearless." I learned by testing tearless dog shampoos in my own eyes that many burn.
I'm glad the groomer called you pick up Geno early, paid for vet bills, and was forthcoming with information. If you have haven't had any other problems with this groomer and you trust these people otherwise, I probably would keep going to them rather than risking unknowns with other groomers.