Anyone here own one of these old firearms?

I have a friend with one that the safety selector lever is missing,he asked me to take a look at it.

For the life of me I can not figure out how the  detent and spring are secured (not by the pistol grip like an AR).

We have looked everywhere for schematics etc but are unable to find any,anyone own one of these old guys or are aware of how his particular part works.

Thanks

Take off the end plate or stock if it’s A2 style, it’s likely hiding there

Edit:  I’m a dumbass and not familiar with this rifle, still could be hiding in the butt stock

Thanks for the reply but......Finally found a schematic for the Bushmaster Arm Pistol (the same lower as the Assault Rifle).It looks like the detent is a Ball type and the spring is very,very short and by design of the lower looks like it's fitted from the top somehow and once the selector is in place that holds it in.

https://youtu.be/33JadSsWyyo?si=Tm_l1BWC-YE8dvYh

You may be in luck if Hydra releases the ARM pistol this year. I am trying to remember how many parts interchanges between the rifle and pistol.