I accepted a book back on 9/19 that eventually got lost in the mail. It went back on my WL and I accepted the request on 11/3 and received the book on 11/8.

Well, today I received the first book that was "lost" in the mail.

I know that the PBS rules state that I should mark it received, which would then take a credit from me and give it to the sender. However, it does also say that I shouldn't mark it received if the postmark was dated a week before the lost date. The package made it all the way here without being stamped (or whatever it's called) so I have no clue when it was mailed.

What am I supposed to do?

ETA: I should also add that I tried PMing them to find out what was going on and I never received a response.

You should give the sender the benefit of the doubt and mark the book received. Since you have no evidence that it wasn't mailed on time, you should assume that it was.

If there is no proof that the book was mailed late, then you need to assume it was mailed on time and mark it as received. Hopefully it is still wishlisted and you can turn it around for a credit fairly quickly.

Did the book have DC on it?  If so, plug that into the USPS site and see what it says.  How about a date on the mailing label?

I agree, if you can't figure out when the book was mailed and how long it's been in the hands of the USPS, you need to give the sender their credit and mark it received in your transaction archive.

Yup, i agree, too.

Thanks everyone! I'll go ahead and mark it received. :)