I think everyone's right. They've already checked out. It's a shame they were so sneaky about it. If they want the spare clothes, let them come for them. You can certainly include the termination letter with them. Like playfelt said, just leave it alone, let the notice time go by and advertise. Even with the notice time, I'd say you probably don't even owe them that. They're in breach of the contract anyway with their own behaviour. You could terminate just based on that.