There's usually a fair bit of "come and go" in folk clubs and our one is no exception.

We seldom sell tickets in advance and it's usually only for shows which we expect to be rather busy.
IF someone buys a ticket in advance and lets us know in good time that they are unable to attend, we would normally oblige with a refund although there's no policy laid down in stone.
However, if they just failed to turn up without any explanation then that's surely too bad. I'd suggest that they would have a cheek to even ask under these circumstances. Of course, even then, I hope that we might still consider a gesture of good will if there really were compelling and/or unforeseen circumstances.

More often, our members and regulars just reserve tickets without charge either by e-mail, phone, or in person the week before. Unfortunately, some of these people "fail to trap" on occasion but, if they don't arrive before we start, we can at least sell tickets to anyone else who arrives.
While we don't lose money as such from these non attendees, it does get a bit irritating as it can sometimes give us a false impression of our likely size of audience.

Arguably, we could insist that all tickets must be paid for in advance or otherwise they can take their chances at the door. That's what would happen in any "proper" theatre or concert venue. They could also purchase tickets through an agency or our own online box office(if we decided to have one!). Then, there would be normally no question of a refund under such circumstances.

We don't wish to go down that road yet although many suggest we should. However, even although we and many other clubs still like to take an easy going approach and "come and go", it should work both ways. Our customers should also try to ensure that they don't leave us in a difficult position either.