My gf keeps telling me about a book she once owned called ‘Sign of the Acorn’, and for the life of me I cannot find it anywhere. I would really like to buy this book for her as a surprise and was wondering if any Dopers could help locate it.
Apparently it involves a brother and sister that get seperated and are then somehow reunited by birthmarks. I think.
Any help would be greatly appreciated, and the fact that the title may be wrong/book doesn’t exist shouldn’t put you off. 
Google comes up with two pages of hits for “Sign of the Acorn” (in quotes), but none appear to be related to a book. You might ask her to consider the possibility that the title is slightly different from what she remembers. “Sign of the Walnut”, maybe?
It fell down behind the cushion of the couch in the living room.
eBay’s got nuthin’, sorry.
Are you sure she’s remembering the title correctly?
Nope, that was why I put the title in quotes, I have always doubted that the title was different and she herself admits this may be the case.
Make that
‘I have always doubted the title was correct.’
Or
‘I have always thought the title may be different.’
There’s a book called The Sign of the Beaver, but the plot doesn’t match your description.
By just googling “sign of the” + book title I came up with that one, plus Sign of the Chrysanthemum, Sign of the Seahorse and Sign of the Unicorn. There are probably others since that was just page two.
Careful. You’re getting furry.