You got halfway into your appointment, and you got shorted.
It doesn't matter what the issue was. Part of the risk of being an agency is that you have to make good when there is a problem on YOUR end. If there are with the landlord or the building or the provider, that's on the agency. They take a 50% or greater cut in some cases, and they expect to get that for free?
Every once in a while you gotta earn that money. This is one of those times.