@KrissyKat
Do we really think that was his personal bathroom, though? He loves his gold toilet, and that room is way too cheap looking to feed his gold-toilet-seat ego.
My thinking is (1) that was a guest bathroom. He wanted his guests to see how many important papers he had from his time in the WH, so he left them laying around where guests were sure to see.
The other theory is (2) that they were thrown in a rarely used bathroom during the attempts to hide them. The logic there being: that would be the last place searched-- Librarians don't tend to look in bathrooms for books, and most rich people don't tend to store papers in old bathrooms, so (Trump's people hoped) the Federal Agents seizing the documents would not find them in an old bathroom.