Yep... I can see it happening. A small cut on the ear (which can happen if the groomer used scissors to trim the hair around the ears) which doesn't get proper attention will need to be trimmed (the actual ear) so there's live tissue that can be stitched. If it became infected, that could necessitate more removal of dead skin/tissue. It could have been avoided had the groomer mentioned the incident to you, which they should have done.

I can understand your vet bills, but since animals are considered property, you aren't going to be able to recover for Angus' pain and suffering nor that of your children.

Good luck.