White outdoor LT 1850 drive pedal loose & not working

[Underwater]

Hoping someone here can help me with this. The drive/reverse pedal on this riding mower just falls loosely all the way down, and when I move it back and forth it feels like it's not connected to anything. I'm not skilled at reading technical diagrams, but I found this, and I believe what I'm dealing with is on page 7:

Diagram And/or PartsList !! White-Outdoor-Parts-Manual-13A4616G190-LT-1650-Year-2003

User Manual: !! White Outdoor Lawn Mower Manuals - Lawn Mower Manuals – The Best Lawn Mower Manuals Collection

usermanual.wiki

When I squeeze my head under there (not a lot of room!) I can see that at least part 51 (drive control assembly) is moving with the pedal, but I can't tell where it's supposed to engage with anything else or what might have come loose. The belt has tension. I did bottom out on some rough ground shortly before the problem started, but then was continuing to mow over flat ground when suddenly the pedal disengaged. Any tips on what might have happened or even how to get in there to look around would be very helpful. Thank you!