This is after the fact, but in future, if some research is done, recommendations are sought and referrals from present clients are availabe are some of the ways to find a good/competent vet.

Other things to do are just during regular checks/vaccination visits - are you comfortable with the way the office is run? Does the vet spend time with the animal (and seems to be trying to build a relationship) and with you? Ask questions - lots of them. If you get the brush off or you're not treated as a caring pet owner - find yourself another vet.

It's too late for this lab - but laying some groundwork with a future pet can save you from future heartache sometimes.