I was ready to package a book when I realized the title didn't match. It's the same author, the same ISBN, but the title is different. I realize I should have realized the title problem when I posted the book, but (to make excuses) 8 of the 10 words in both titles are identical! I'm sure I glanced at it and thought it was the same. My fear is that there is a book that goes by this title, and that the requestor is looking for that book.

I couldn't find a way to PM the requestor, (I'm not so used to out-of-the-ordinary PBS, still!) so I cancelled the order, hoping I'd be given a prompt to choose to PM the requestor. However, I didn't. So I'd like to contact the requestor somehow and let her know what is going on and give her the option of getting this book if it's the one she wants. Any suggestions?

Check your transaction archive.  There should be a PM button there for you to contact the requestor.  However, the request may have already been sent to the next person in the FIFO line.

since you have cancelled it you can find the requestor in your transaction archive like Sheryl stated.

however, before you cancelled it (and as long as you had accepted the order) on your main page under "books to send" or something like that you could have PM'd the requestor.  the button is in the upper right of that box for that book.

Thanks, y'all!