@Dave B. It seems there are a few pieces of information missing here. Assumptions were made. So perhaps the responses you've received already will fit your situation or they may not. Please clarify:
- Is the tenant on a month-to-month rental agreement or a lease with an end date? If the latter, what is the date the lease ends?
- Is the tenant's rent paid up through the current month (April)?
- Are the tenant's utility bills paid or will the father pay those?
- Does the landlord-tenant law for your jurisdiction allow "no-cause" termination of a rental agreement?
If you received rent for this month (April), then your tenant still has right to possession of the unit at least until the end of this month. You can't evict for non-payment of rent or declare abandonment at this juncture. You can't change the locks. If the tenant gave his father the keys and permission to retrieve his property, you can't stop this. It's good the father has been communicating with you. Hopefully you'll hear directly from the tenant too.
If your tenant didn't pay rent for this month (April) or is in arrears for previous months of non-payment of rent, then you should serve the proper notice for non-payment of rent, such as a "Pay Rent or Quit." This is the precursor to eviction. Try to get payment of April rent from the father if you can. You still can't change locks at this time because you will not have legal possession of your unit until the tenant voluntarily returns it to you (part of a good move-out plan) or a court returns possession to you through the eviction process (a long and costly process).
If your tenant intends to not return (obviously) then he or his designee (father) will need to settle things with you. That's why I mentioned a "move-out plan". The move-out plan does not ignore the terms of the rental agreement/lease. Voluntary move-outs are much better for all parties concerned. Proper notice to vacate varies by jurisdiction. In our jurisdiction it's a 20-day notice, but in most jurisdictions it's a 30-day notice.
"No Cause" termination of a month-to-month rental agreement, if allowed in your jurisdiction, can start the process to regain legal possession of your unit sooner than waiting "for cause". In the case of a lease, it will end when the term is up, or the lease is broken, or the tenant is evicted "for cause."
If you know the whereabouts of the tenant, it will not be a case of abandonment, so abandonment procedures wouldn't apply. A tenant can be legally served while incarcerated. You may also be able to verify the tenant's intent to end his tenancy and his wishes regarding his personal property. Work with that.
Yes, you are entitled to compensation according to the terms of the rental agreement and the law for your jurisdiction. You are also allowed to negotiate a faster move-out which may result in less cost to you and less damage to your unit. I'd go that route and make it easier and less costly for all parties concerned. Your goal should be to regain legal possession of your unit as soon as you can, with the least amount of monetary loss and the least amount of damage to the unit. Then do your turnover (make-ready) for the next tenant and rent it as soon as possible to a qualified and responsible tenant. All is not lost.