OMG poor baby. I would say a vet visit also get it documented and call the groomers. The least they should do is pay your vet bill. I cannot believe they didn't mention it...what in the world did they think, you wouldn't notice
I don't use scissors on my babies ears and I do their grooming myself. I use a tiny pair of clippers. I would be scared as careful as I am of cutting them accidentally.
Hugs to you and your baby for having to go through this.