Phones on shop floor

Asking for a friend who works at one stop. They may have been caught checking the store group chat whilst the shop was quiet on the shop floor, in search for extra work at the other branch down the road. They are temporary for 5 months and are worried that they will fail their probation. Is it that bad, what will happen? As long as they don’t do it again and leave their phone in the back it should be all good right?