Yup. I know we've talked about how frustrated it make us. I don't know if there is anything you can do about it. It's not exclusive to seahorses, either.
When I worked in a fish store, this happened a lot with many fish. I never did figure out a good answer. We actually had authority to tell people 'no', and they'd either come back another day and lie (Why, I remember you?), go to a different employee and see if they'd be more flexible (some didn't care unfortunately, but some did), or they'd complain to the manager. He would almost always give in, even though it was the person that made the policy. I suspect many went to different stores too to try and "game" the system.
Which is something I just don't get. It's probably been too long since I've been a novice, but it certainly seems like a lot of people try this. Not every new aquarist or not even the majority, but a big enough minority that I don't know what we can do to change that. It is something I do want to try and figure out the mindset behind it, in hopes of figuring out how to address it.