Ah right. Fuck knows what's happened then. If I were to glue the pedal back on (assuming I can force it back on), which glue is the best to try? Cheap nds crank and pedal isn't a bad plan b though!
I had a similar problem once. A friend who is an engineer suggested
threading the pedal on the back of the crank in order to cut a new thread.
I tried it and liberally applied loctite - it seemed to work for a while.
Pedals are L/R specific so you can’t put them on the wrong side. If this has happened on the NDS you could find a secondhand arm and pedal cheap?