Turned out that the lead shielding between the walls ground wire was disturbed during a service call on it. Nurses freaked out knowing they had been being exposed for nearly 2 months.
The lead on the back of the sheetrock doesn't need to be grounded for it to shield x-rays. Lead does that just fine all by itself. If the framing it's mounted to is wood and not metal studs- which would normally be automatically grounded by virtue of electrical boxes being mounted to it, it probably is advisable to provide a ground for it since is a metallic "structure" that could become electrically energized. So it's an electrical and NEC thing, nothing to do with preventing exposure.
You might want to tell the nurses that if the radiologist hasn't told them already.
-Hal
