MH rear bathroom mirror fell down!

[Astrodokk]

Luckily it didn't break but it sliced the vinyl on the toilet seat. So I'm examining the design, and it's kind of screwy. The mirror sits on a piece of thin plywood that is hinged on each end, with thumb nuts behind the wood that can tighten it in the "up" position . Why would it be hinged so that it opens "up" and be allowed to be tightened in that position? Under the wood is a flat wall. I'll be using mastic to reglue it back to the wood unless I find out that it shouldn't even be there.