I am so sorry for your loss and for your situation.  Here is the thing: only someone who is authorized to represent the estate can sign an authorization for the release of the records from the rehab facility.  So you really do have to reopen the estate and the executor or executrix has to obtain a current Letters Testamentary to submit with the authorization.  Look a it this way: if you find that you have the basis for a lawsuit then you will already have done the necessary by opening the estate.  The personal representative will be the one to bring the action on behalf of the estate. Good luck to you.