This is a question for a lawyer and/or religious advisor, not an advice columnist. First, because those people have the specialty knowledge to answer the question from their area of expertise, but also because conversations with them are privileged and confidential - and there's no written record pasted all over the internet. I don't care if it doesn't have your name attached, it was a dumb move.

If LW is legally obligated to return the comic to Brother, which LW might actually be even if they've got the written evidence that he said "do what you want with [the desk]", the last thing they want is to have any sort of evidence of their shady shenanigans floating about.

If they'd spoken to a lawyer, now, they could've then done what they liked under the assumption that nobody could ever figure it out. Now there's a teeny tiny chance somebody will figure it out. Probably they're still in the clear, but still.

In conclusion, never ever put it in writing.