The Churchills should know better!
I think that Bailey (yes, I remember Bailey.) Probably went to the library, then put the book down, picked it up, and put in in her inventory. It goes something like that.
That happened in Riches Galore (Schipperke's story).
EDIT: Sorry, I think I've pretty much said what Pam said.
BTW, Mars real Estate Do's and Don't's is worth about §1000 (?). Sell it, and forget the whole thing happened.