You can glue it back it. Need the crystal cement.Howdy again Sir!!Agree with the crystal side solution. Another possibility is that the crystal can be removed with a crystal lift. Is there a cylindrical area on the outside edge of the crystal?
Here are some examples of such crystals:
The crystal lift grasps the cylindrical section and squeezes it in, loosening the edge of the crystal from the groove in the case. You can google Crystal Lift to get an idea of what I'm talking about and a cheap one (Esslinger, $15) is adequate.
While attempting to clean the upper bezel ring with the crystal in it, the crystal decided to become detached. I am supposing my previous optimism about crystal lifting and such was premature. Thanks for the google idea.