@Stephen983 Is this a refund you sent the guest through the resolution center, or a refund they feel they are due by Airbnb? If the former, you could contact Airbnb to say that you sent the guest $, but they say they haven't received it, and ask what's going on with that. If the latter, that's between the guests and Airbnb- they won't give you private information like that regarding the guest's account.
Also, refunds are not given in the moment a guest cancels- I think it can take up to 2 weeks for it to be processed (Translation: Airbnb likes to hold onto everyone's money as long as possible.)