As someone who has been fobbed off by receptionists and nurses etc and knows how it feels, I would say keep at the vet until he or she explains it all to you fully, both before and after the test results. I hope it's something that they can find a good solution to and take care of yourself tonight, worrying about Arwyn. Sounds like you'll have to make an appointment to collect him, so hopefully the vet will explain it all to you with the results then as well.