Have you encountered a scenario where you have to deal with a very upset guest for something that wasn’t your fault? How did you handle this situation?

Stay calm and Don’t let your emotions get the best of you.

It's part of the job to go through this experience, all you have to do is to take responsibility and do what is necessary to resolve the issue. When a customer says 'you', s/he is referring to the Company you're working at. 

First of all you have to clam him down and show why the issued happened and how will it be solved without going into deep details and make him feel that the company will do anything in order to solve his issue and promise him that this will never happen again.

After all this and when the issue is solved contact him back to get his feedback and thank him for his waiting

I had to deal with this often when managing the Keystone Pipeline people coming in and saying why is the pipleing going thru his property and not mine ( Money was involved) explaining I learned to also make them laugh! When they understand you are helpless in the decisions and you can not change it but you can tell them something that gives them laughter and maybe self worth the you are doing your job well!

yes I did.I answer her politely ans tries to give the best solution to her matter

When that situation occurs talk softly to guest and describe his or her specialties as we can say that for maintaining the situation we talk about general topics and and lastly try to convince him or her about your good thinking for him or her.