Former roommate - stole and left - anything we can do?

Three of us living here. One guy starts sleeping at his girl's place every night. Leaves high and dry Tuesday. He does not leave the key, though. I call my lawyer and he advised us to email him requesting the key, garage opener and a portion of the October rent. We send the email. He comes and he puts the key and opener on the ground in my room. What is missing in my room, though, is on my desk the other roommate's rent (cash) and the lease agreement I had opened because I was reading it to my lawyer the night before.

So, he has the only signed copies of the agreement. I own the house and rent out my spare rooms. It is virtually impossible to prove he stole it, although we know he did. My question is what about the lease.The three of us are the only ones who know it exists. Did him stealing that mean he beat us on this one? All we have now is texts showing he made payments and paid a deposit and Sept. payment.