I sent out 2 books on 8/9, and another on 8/10. 

One of the 8/9 books and the 8/10 one has been marked received, but I'm worried about the other 8/9 book.  I realize that it's not unusual for a book to take longer with media mail, but I got DC and it has no history.  My post office never scanned it in.

Does this mean it's lost?  I've used DC for all but unpostable only orders, and I've never had one where not even the initial post office scan showed up.

I guess there's nothing I can do at this point but hope it shows up eventually, right?  Or is there some way I can check on it that I don't know about?

Sometimes they don't scan them at the front desk. I always make them (this was when I bothered with PBS DC) but once Hubs mailed a book for me and the man said they "would do it when it went on the truck"...which they didn't. The book got there safe and sound but I did not get my credit instantly.

Yes, this has happened to me.  I almost always put DC on mine.  But my PO (the main PO in the county) doesn't always scan them in.  Then it has to go to Richmond and sit for a while and maybe get scanned in there.  It seems to take forever.  I just hate seeing a blank USA map.  I really prefer to mail out of Alexandria because then the books go either to the hub in MD or to the Dulles hub and it gets scanned and sent out so much faster.   But don't worry - they almost always show up sooner or later.   I've had them take a couple of months!  They were declared lost!  And I'm amazed that some of the time (like the 2 of yours)  actually get there in a very short period of time.  That's always a nice surprise.

Ruth

Same thing here...mine are always scanned when the po recieves them, but I have one out there that have no scans...hopefully it will get to the reciever shortly.