If you don't see RADITHOR_PT_BEOX listed as missing when loading the save, then you have it. It may not be called beox though. The element's identifier and its name are two different things.

If you "run" elem.RADITHOR_PT_BEOX in the console and you get a number, you have it. Then you can try running element.property(elem.RADITHOR_PT_BEOX, "Name") to get its name, which is the name !set would understand.

Then they're probably set as ctypes or other type-carrying properties of existing particles.