I've found few dogs I can't handle, it's usually the parents that are the problem and I would like to know if I'm walking into a situation where someone is difficult. I had an especially bad experience this week and wish I'd had a head's up on this guy because I would have either turned him down or been much more prepared for his total angry melt-down in my living room.
Sitters aren't given an option to see other sitters reviews or comments written about dogs or their owners. At best even if we did reviews are subjective. Dealing with difficult clients can be a challenge, all you can do it provide quality care for the pup and to understand the requirements of the client; best of luck in the future.
Walt is correct. Did you do a Meet & Greet? I require a meet & greet and ask questions about the dog. I listen carefully to the owners' answers. The dog may be a great fit but if I feel the owner isn't a good fit, I will encourage the owner to contact other sitters also. I have let customers go if I see there is a potential issue. You didn't say what the issue was but that is "your" home and you are in charge of your business. Sometimes it can be difficult but stay calm, be professional but firm. Consider it a learning experience.