Hey, many thanks for this thread!
I had the very same problem, where the '''mounting mechanism''' retracted back inside the back of the display as the latch that locks the mechanism in the "out" position was not engaged properly when I was taking the 8 small screws out.
I used the '''paperclip method''' with a pair of '''needle nose vise-grips''' and it work no problem. It was a bit difficult to get the right, bent shape of the paperclip to thread it through one of the screw holes of the actual mounting mechanism, and then back around and out of the opening in the back of the display, in order to grab both ends of the paperclip with the vise-grips. I used a '''regular pair on needle nose pliers''' to get inside the opening so I could slowly tease the paperclip around and through the opening. Once I had the paperclip threaded properly and had locked the needle nose vise-grips on to the two ends, I needed some help in the form of an '''extra set of hands''' to actually '''pull the mounting mechanism back out'''; one person to hold the hold screen in place and to use a cut credit card to insert and press the '''latch release down''', and then another set of hands to hold the vise-grips and pull the mounting mechanism back out of the display. I did have to use '''quite a bit of pulling force''' to get the mounting mechanism back out and into the locked position.
Then it was easy to reattach the mounting bracket and use the card to release the locking and retract the entire assembly back into the display.