I've bought a couple of mics at GC. I'm in California.
The first time, I was told about the no-return-due-to-health-reasons policy cited above. I bought the mic anyway; no regrets, so it wasn't an issue.
The second time, I was shopping for something else and was just asking questions about a mic. The salesperson picked up on my interest and was pretty aggressive in trying to sell me the mic ... I was hesitant and said, "well, yeah, but if I don't like it, I know that your policy is no returns on mics due to health reasons". The salesperson responded that I could return the mic if I didn't like it. And of course, given that I had heard a contrary statement in the past, I said, "willl you put that writing?"
He did. I have a receipt that says, in writing, that I could return the mic within 3 days if I didn't like it.
I ended up keeping the mic because I did like it. Coincidentally, it was a BLUE mic.
But GC's policy of no returns for health reasons is pure BS.
If it serves them to let you return a mic, they will let you do it.
So don't think that, just because you bought a mic at GC, it has never been breathed/spit on by another person.
Then again, you do use a pop screen, don't you? That can easily be sterilized with some rubboing alcohol if germs worry you.