Escape window screen won't stay on

[RogerR]

I have a 2017 195RB. The emergency escape window near the bed tilts out from the bottom and has a full size screen. I bumped it and the screen fell out. There was a small piece of plastic about 4 inches long laying on the floor.
The screen has two red knobs and fits in the two notches on the bottom of the window unit. But there is nothing at the top to hold it in place.
I assume the piece of plastic did it but after 1/2 hour of struggling I could not figure out how it would be attached. My wife tried, same result.
We are heading down to Florida and will need the screen on the window.
I can take a picture tomorrow of the piece and window if someone can't suggest a solution.

[RogerR]

Here is a picture of the screen that won't stay in and what I suspect is the piece that should hold it into the frame.