We had luggage "misplaced" but not the way you are talking about.
We did our own transportation. So we dropped our five pieces of luggage at the port, and they arrived at our room shortly after 2:00. At 11:00pm the night before we left, we left them outside our stateroom to be picked up.
We debarked and got our luggage to clear customs. One, two, three, four...hey! Where is the fifth peice of luggage? We looked all over, no bag (didn't help that it was a black rolling "maximum carryon size" bag). We ended up filling out a loss report and leaving without it (it was laundry). They said if they found it, it might make it on our plane (they had our information), or we might be paged at MCO. But we didn't get paged and when we got to our own hometown airport, it didn't appear on the carrossel. When we walked into our home, our answering machine had a message on it from a luggage service manager for Delta in Ft. Wayne, Indiana. (We flew Northwest, direct from MCO to MSP). They had our bag. Delta kindly put it on a plane to Minneapolis and then (even nicer) had one of their luggage service staff in Minneapolis drop it by our house.
Apparently, our black carryon got set with the luggage for another stateroom, where that stateroom had lost their tag. They grabbed ours leaving, checked it in through Ft. Wayne, then discovered they had the wrong bag at the airport. So it wasn't the airlines fault.
DCL had our stateroom listed as "missing a bag" when we picked up our luggage, so the people who grabbed our bag weren't completely at fault, either - although had they checked the tags while they were debarking, they would have left our bag - our case was labeled with both my business card and our yellow "chip and dale" DCL pick up tags.
(Then again, I got to luggage pickup in SF once to find a woman going through my underwear in an attempt to figure out of my bag was hers! Excuse me? Check the tag - or at least say "hey, I don't wear this size/color/brand/style of underwear before you have half my bag emptied!)