The ball bearing is trapped between the aperture ring and the rest of the lens. On a Pentax lens, there's a hole with a spring inside, in the lens body. The spring puts pressure on the bearing to hold it against the aperture ring. Here's a Pentax-M 50/1.7. The bearing is just above the orange diamond, stuck on with grease here. When it falls off, all you see is a hole.
The aperture ring usually has teeth on it that make the ring click at each stop. The teeth show where the bearing should be, so if you have the ring in the right place, the bearing should be opposite those teeth. Here's the ring and the teeth from the same lens:
I've seen one other arrangement where the teeth are parallel to the lens mount, not on the side.
I have no experience with that Sears lens. The front element may have been held in by tiny set screws on the side that you didn't see, and you forced it off. Now those scfrews are ineffective so it seems loose.