A screenshot of the booking will be irrelevant if Marriott decides to close the OP's account, cancel all reservations and confiscate the points. It's not like a paid booking where one arrives with the intention of paying some cash amount - and therefore something can be worked out if rooms are available - it's arriving and expecting a free stay, which no hotel will do unless Marriott is reimbursing them.

I would definitely have a Plan B in mind in case the hotel insists that no award stay is possible.

Sometimes OPs in this situation know they've been misbehaving --> so might as well try to take advantage of one last points booking before being shut down. And other OPs might not have a clue what's going on and would expect the block to be temporary --> so no need to overreact. So either way it's probably worth trying to check in.