What if tenants don't cash security deposit check?

[Stacy Tring]

Three people signed the rental agreement, which states all tenants are joint and severally liable. It also states that any security deposit refunds owed will be made payable to all parties on the lease agreement.

One tenant has stopped contacting the roommates and us, and we are not sure they are planning to return. We do not suspect foul play because apparently that tenant's relatives have reported to the remaining tenants that the MIA tenant has moved in with another relative (but did not give that MIA tenant's new contact information). 

Our local statute specifically says: "the tenant shall not be considered to be absent from the dwelling unit without notice to the landlord during any period for which the landlord has received payment of rent." Since the remaining tenants have still been paying, I'm not sure that I can treat the MIA tenant as absent.

Let's say the remaining tenants decide to move out (probably because they will eventually have trouble paying) and I make the refund check payable to all the tenants per the rental agreement (and to protect myself against claims from the MIA tenant), but they can't cash it because they can't reach this third roommate.

Any recommendations on what to do with the money or what course of action to take? Thanks in advance.