... I guess I have more of a first-name
relationship  with the Postmaster of the PO where
I buy MOs, and so when he says it'll be handled by
them, I trust him.  So my experience was
straight-up and uncomplicated.  

I could imagine other POs in my area where it
might be handled in a less professional way. 
There was one that gave a package addressed to me
with a delivery confirmation notice attached to a
carrier.  He ran his route and came back to the
PO, bags empty.  When he saw in his paperwork that
he still needed to clear the delivery
confirmation, he took his end of the paperwork,
scanned the package as delivered (I mean ... he
must have delivered it ... because he
didn't have it any more ...), and knocked off work.

The package (fortunately it was a cheap CD and not
a wishlist cel) never turned up, and my complaints
to the PO involved got nary a response.  But I'd
guess my carrier got promoted to MO investigations
at your location.

Poop happens ... but given the PO's normal way of
handling this, it doesn't have to, and even by
your experience usually doesn't.