I have seen no comment that this renter is "active" on the DIS - and even if they are, the transaction was not conducted thru the DIS (per the OP's admission) and we are hearing only one side of the issue. The OP has not asked for help and has not provided the username of the renter so there is nothing we can do based on the situation.
Do you truly feel the DIS has any responsibility in this situation? We don't even know how the OP transacted the rental - thru another site, eBay, Craig's List, etc.
Hopefully, the poster can find some resolution, but there is little the DIS can do to assist with such a situation.
Completely understand, it was just a thought...