Not worth it, they will end up voiding it. There are plenty of threads about this happening.
Had you actually called up the book and informed them of this, there's a good chance they would have given u a free play ( i know it's happened to a couple of guys here, can't remember who)
Most books would have given you some free credits in your account if you had called them to let them know of the mistake. I was credited $25 twice by 2 different books for calling in bad lines. It's the right thing to do, anyways. Bad Kharma to try to cash in on a mistake by the books, IMHO. But Beantownjim doesn't believe that, I guess