[JRTJH]

While sitting, reading this post, close your eyes, hold your arms out to your side "neck high", slowly bring your arms to the front and attempt to touch your index fingers together....

Reinstalling that "valve dump handle" is the same concept. You'll be working "with your eyes closed" and trying to "anticipate/feel the right spot"... It's not as hard as you might think, and actually, if you pay attention, you can "feel the empty fitting" with the rod as you explore. Once you find the right spot, just turn the rod clockwise until it's tight...

Alternatively, you know how long the rod is, you know how much "stuck out before it fell off", so lay it in that position and you can "estimate where the fitting is"... Cut a "U" shaped opening in the coroplast (with the hinge side toward the front) and pull down the flap. You'll see the fitting right in front of you. Once the rod is reattached, clean the coroplast with alcohol and close it with either SCRIM tape or with Gorilla Tape.

If you want a "more permanent repair" you can consider using some "Thread Lock" on the threads before reattaching the rod.