Are Either of Required to Pay for This? Thank you

A sub contractor who sells for us signed an agreement with our name on it to participate in a home show, the cost is $1,995. We did not ok. When they came to us for payment i explained that the subcontractor was not approved to sign for us. In past years we allowed it, this year everyone assumed. I explained to the situation to the HOSTILE home show people, telling them that the past was the past and it did not create a legal precedent. Finally i advised that all they had was a piece of paper with the name of our company with a signature of a subcontractor........PLUS two days PRIOR to his signing the contract, I notified the Promoter that we were not going to be involved in the Home Show. Today the subcontractor received notification from a collection agency that he is responsible for payment as he signed where it said," I am duly authorized to enter this agreement and personally guarantee the same". We are in FL, the contract says disputes venue will be NY.