Taking off metal jewellery in the scanner is about the worst thing one can do - it’s then loose. It would be very unlikely to move from a clenched fist, even if

Taking off metal jewellery in the scanner is about the worst thing one can do - it’s then loose. It would be very unlikely to move from a clenched fist, even if ferromagnetic. However having it escape your hand isn’t that difficult. I’ve seen most these things play out. And as you say, it’s exactly what the call bell is for.