I've heard a lot of stories about guys losing the tiny ball bearing and spring safety parts from their Crosman 22XX/13XX guns when they do some mods to the trigger. I have yet to lose either and I have assembled/disassembled my guns MANY times now. Here is why I haven't lost any so far.
When you want to work on your trigger, remove the entire grip frame from the air tube while holding the gun in the upright position. It's only 2 screws that hold it on to the action so it's simple to remove. This one extra step and you will never lose one again due to it flying out of the grip frame once you remove the cover. Once you have the grip frame off you will see the top of the safety spring with the ball being underneath the spring. Cup your hand over the spring and tilt the frame upside down and out slide the spring and ball, gently into your hand. To reassemble place the ball and spring in the little slot on top of the frame, once the cover is on the frame and you are ready to reassemble. Attach the grip frame back on to the tube with the 2 screws while holding the frame to the air tube.
I have yet to lose one using this method and it's only one extra step to do it. I hear of guys using dabs of grease and stuff to hold them in place, but why bother to put any gunk in there when you can easily remove the frame and take the tension off the spring? Easy solution and it definitely works.
Now go do those trigger mods and don't worry about that little ball and spring anymore!