If a receiver doesn't receive the book within the PBS time frame, and the system marks it lost, what happens? 

Does it go back on your WL and you get the next copy?

How long after it goes lost can a receiver go back to their transaction archive and mark it received?

Yes, the system either orders another copy for you if one is available, or it goes on your WL at the #1 spot.  I believe you can mark the book received forever and ever, the option should never go away.

It doesn't order another copy for you if it's gone lost if it's not a WL book.  IF it's a WL book the it goes back on your WL in the same spot you were before.  If it's not a WL book then it goes on your reminder list-PBS suggests you wait 2 wks before reordering incase it shows up.  Of course if it's WL and gets offered to you before then, then you risk getting 2 copies. 

That's not what I wanted to hear, Mrs Lefty!

Several weeks ago, I had a massive post office outing. I brought a few mail-order returns, PBS books, other books, letters my dad needed delivery confirmation or certified. Lots of stuff.

I got a PM from receiver #1 and she didn't receive my book, it had been 2 weeks. I poked around, and found that I neglected to mail it. No problem, I mailed it the next day in a prioriy flat rate envelope, she got it in 2 days, all is good in the world.

While looking to see if I mailed her book, I went threw all my tabs to make sure I had sent everything I was supposed to.  I thoroughly checked and was confident that all really was good in the world.

A week later, I get a PM asking about a 2nd book. I though receiver #2 was being impatient, bc I had already gone through the double checking ordeal and confirmed that I did not possess any book that I should have mailed.

2 or 3 days later, I find receiver #2's book. PM her about my error, and sent the book UPS. The book went lost on Tue 5/12, and she received my copy on  Fri 5/15.  She said she will buddy me the credit when she gets another credit.

My concern is that since I told her it would be sent UPS and sent her the tracking number, she new it was on the way. So, I can't decide if she "spent" the credit that was returned to her for my book, or if when it went lost, she was offered a 2nd copy of the book (it was a WL book) and she accepted the 2nd book.

I realize that ultimately, this is my fault. If I had been more organized, I would have sent the book on time and this problem would've been avoided.    Now I feel like this is one big complicated mess.

She shouldn't be buddying you the credit if there was only one copy of the book on the way.  She should mark it received via the transaction archive.

The system will then give you a credit for sending the book, and her account will go to negative credits if necessary.

From the help docs:

When a lost book arrives, you must mark it received.

To do so:

• Go to your Transaction Archive:

  • From My Account: click the link "Transaction Archive" in the yellow bar at the top of the page
  • From anywhere on the site: place your cursor over My Account in the toolbar at the top of any page on the site and choose Transaction Archive from the menu that drops down
• Sort the Transaction Archive by "Requested by me" - "Lost in mail" - "Title" - "Descending"
• Locate the Lost transaction for this book in the list.
  • If there is more than one Lost transaction for this title, check the sender's name on the right of the transaction against the name of the sender in the return address on the package you received.
  • Click on the transaction.
  • The next pages are the regular Book Received pages:
    Click on the next page
    Provide more information about the swap on the next page
    • you will also have the option to send a message to the sender of the book
    • you will also have the option to provide comments on the swap that only we will see
• Both your account and the sender's will be updated when you have done this.

The book will have been placed on your Wish List when it was declared Lost, so you should remove it from there if you do not wish to be offered another copy when it becomes available.

Lost books must be marked received when/if they arrive, to keep your account in good standing.

If the book has a very late postmark on it and you have re-requested it and you will end up with 2 copies, see My requested book arrived with a late postmark! for information.