Thank you very much for your answers. I did not make clear that the mobile owner was not located, picture a bunch of SLF to stare at the F/A without a reaction. So the guilty was not located!
And one more question: how can a F/A can confiscate a mobile? He or she can ask the offending pax but it can and would be ignored! What can you do in that case!
Thank you for your patient with all SLF.
Rwy in Sight