Yeah the mri magnet is always on, 24/7, you literally can’t store them there. I assume when they lost electricity they must have quenched the magnet (released all the helium that keeps the coils in a super cooled super conducting state). That’s the only way to actually turn it off. Very expensive and time consuming to get going again after that too. If those were in the room before the mri magnet was quenched, well, they wouldn’t be very useful as guns any more, and the mri machine would probably be totaled too. So most likely any metal in that room would only have been put there recently. Go look up mri safety videos if you wanna see what happens when you bring metal into the room.