'98 Altima wiper drive shaft

Good Morning,

The driver’s side wiper on my '98 Nissan Altima stopped working, but the passenger’s wiper still worked and the motor sounded fine. After popping off the wiper arms and the plastic cowl I saw that the drive shaft for the driver’s wiper had popped off its coupling (cog?) near the middle of the vehicle. I popped it back on and the wipers are working. My question is this: Is there a nut or retaining ring or something that should be keeping this drive shaft in place? Or is just popping it back into place enough? I searched around for an escaped nut but didn’t find anything.

thanks!

-Rafael, Cambridge, MA