Thanks for the reply. I agree that I am partly at fault, which is why I'm struggling. I don't feel right demanding they pay when I contributed to them missing a second month by not raising the red flag by noticing I hadn't received that month's rent. I could go back and forth regarding blame, but either way, I am partly responsible, which I totally accept.
I also agree that the best course here is to probably eat half of it and hope they see that since we're both at fault, that it's a good compromise. I mean, I would never send a money order and not track it to make sure it wound up where it was supposed to.
As for how it's gone missing... that's a whole mess. They still have the receipts/numbers from the money orders purchased at the post office so they were able to track them, as was the post office. After they were purchased, they were filled out, sealed into envelopes and mailed to me via certified mail. The money orders were altered and cashed by someone else. So if they weren't taken within the post office, TWICE, where were they hijacked? They never made it to me, and were not taken from my mailbox. Plus they're obviously working with someone at a check cashing place who is allowing them to cash them because there's no way they're altering those things and you can't tell.