l'll have to go down later or tomorrow, hurting a little too much now. I took a picture of the lock and blade, but it didn't take??The top right drawer should just have a cam, maybe cam w hook, to hold it closed. What part of the lock fell apart? Did the core come out, the whole lockset came out, what exactly?
I wonder if it's just jammed, as without the lock and cam....
13,14,15 are the mechanisms. Yes, the rod should be twisted. There are flats at the tip of the rod, so you can stick a small wrench in there to grab the rod to twist it, I want say 1/4" but it's somewhere around there.
This video shows the channel in the back that the rod lifts. Which is why turning it upside down works.