Friend died intestate, brothers & sisters inherit. They

Friend died intestate, brothers & sisters inherit. They expect to abandon the real estate, and personal property, including bank accounts are under $50,000 and they may seek that. That's background. They are out of state and as a long-time family friend I am helping. I have all his paperwork, etc. That's background. My specific issue is this. I found an uncashed check for almost $1,000 from his mortgage company to pay him for surplus escrow funds for 2018. It is dated late January. I also found a large unpaid property tax bill. I stopped at the bank and told them about both. They said that the property tax was paid out of escrow, but the county treasurer still sends the bills to the homeowner. Later they called and said that their attorney said they could take that check back and apply it to the unpaid mortgage/escrow. As I said, I believe the family intends to abandon the property and leave the bank to foreclose, which will come out OK for the bank, as their mortgage is $21,000 and the property is worth about $30,000. My specific question is whether the bank can do that? I had intended to just deposit it in his checking account (at another bank) and should the family try to deal with the personal property they could access it. Personally, I'm happy to let the bank have the check but yet I don't know if the bank can legally do that. The family is pretty hands off, at least at this point, but are relying on me to do the right thing, and basically rely on me to know what IS the right thing. What is your advice? Return the check to the mortgage company, or deposit it in his checking account. By the way, the checking account I refer to is his personal account, which has not been closed.