Definitely!!! You do have the right and need to know what happened and how it happened. If this is a situation where the tech slipped up and didn't say anything, the vet needs to know so the situation can be addressed and any appropriate action taken. Insist on talking directly to the vet, something like this reflects negatively on his (her) practice. I would also recommend that you bring the picture you posted of poor Pouncer's ear. A reasonable and completely honest explanation is unquestionably required here.