I had 2 books in a series on my way to me. I received #2, but not #3, but I accidentally marked #3 as received. And it still isn't here, it was marked as mailed on 3/16.  

Is there a way to fix this? I've had the worst luck with the books in this series, it took me over a month to get #2, the first one I ordered never got to me so I had to wait for it to time out before I could order a new one.

i believe if you use the "contact us"  button they can fix this for you.

From the help documents:

If you marked a book received accidentally from the En Route to Me tab in My Account:

• This book was marked mailed; chances are that it will arrive.
• Please wait for your book; most likely it will arrive and you will have already marked it as received, and won't have to do anything further.
• Please try to be very careful about which books you mark received.

If the book arrives with a problem then you should contact PBS :)  Don't do that before hand, because there isn't anything that the PBS team can do.  They say in the documents that the software doesn't work that way.  :)

Okay, so I'll wait another week or so before doing anything. Thanks!

They won't do anything until either the date for the book to go lost passes (26 days from the date it was marked sent) or until it arrives with a problem. Then they might. I don't know that they absolutely will, I don't see in the Help Page on "accidently marking books" that they will actually do anything. They do state that the process is not reversable, and I don't know if they will get involved to get your credit back if the book arrives damaged any more than they would if you'd marked it RWAP. Nor do I think they will change the marking from a successfully completed transaction to one with a problem if you marked it and it does arrive damaged.

But, you are always welcome to use the feedback form on the Contact Us page listed under the Company column below and ask. But, do not do so until after the date that the book should go lost, or until it actually does arrive damaged, because until one or the other of those happens, they definitely will not do anything. HTHs

I don't think it's fixable--but hopefully it will show up.  3/16 isn't too long ago yet, it may show up in the next few days.

Just be patient Amy, most likely the book will arrive soon.