AM I IN TROUBLE?

Good day,

I really need your advice. I was asked by a friend of mine who is a contractor to work as his assistant so I agreed. Now because he was a very close friend of mine I trusted him until our first client gave us the downpayment. He did not pay me so I left and looked for another job. After 3 months, I found out that my friend the contractor was having problems with all of his clients. The clients were complaining that the jobs were not finished, yet the contractor was already paid. Because of the long delay of the jobs, the clients asked for a refund but the contractor doesn't have the money anymore. Now my problem is, since I was his assistant when the first client gave the downpayment, the contract that was given had my signature on it. If the clients are going to take legal action against the contractor will I be charged as well because of my signature? What are the sanctions? And what should I do so that I wouldn't be sanctioned? I hope you guys can help me out. Thank you.