It does look like yours simply came loose from the wood top cover. You'll have to look to see if the pin is there, or if that is what fell out. There is a small hole drilled in the edge of the back side and that is where the pin goes.
This shows the location of where it attaches to the top cover, and how it feed through the pulley.
And how mine attaches to the tray - yours is not identical, but the mechanics are the same.
I normally have to "help" mine as that back flap doesn't like to fold back quite like it should, not a big deal and may just need cleaning.
This is the back edge - see the little screw head that is in between the railing? that is the back end of the pin that holds the cable. I have not taken one out, so don't know what it's like.
