1996 Geo Metro door hardware problem.

The window has fallen out of the track of the door
regulator. The car was sold to my wife with the driver font door handle removed.

I removed, lubricated and replaced the door regulator. It works fine. The problem is the window does not stay in the track. I know very little about how a regulator works. I assume the track silides along the bottom of the window as it is raised or lowered. THERE IS NOT A RUBBER GASKET IN THE
GLASS TRACK OF THE REGULATOR OR ON THE BOTTOM OF THE WINDOW ITSELF.

Any advice you can provide is greatly appreciated.