I think you did fine.

Here's my thinking:
- You knew they were $34, and you were happy to buy them at that price.
- You don't actually know the outcome. The woman probably didn't get the discount. If you had waited, you might have been frustrated for waiting around for nothing. Plus, it would have taken even longer, since you had already paid... it wouldn't be as easy as just ringing up a different price, right? They'd have to figure out how to refund your money, then ring up the new price, etc.

I think it would have been a lot of hassle, for something that probably didn't even happen, and for something that you weren't particularly bothered by to start with. So yup, good call.