You had a "jobsworth" on that flight. You should write a snot-o-gram to he airline and complain. Unfortunately, there are a lot of morons in cabin crew management and they like nothing better than trying to wind up passengers be enforcing pointless rules which these idiots try and explain "are for safety". To be honest, I don't know what the risks are to the aircraft with mobile phone useage in flight, but I do know that it is very irritating to hear phones "hunting" for a signal when in flight. As for my flights, I tell my passengers that they may use their phones during a ground delay and that they may walk around untill we are ready for departure. Also, if an extended delay is expected, we'll also arrange for water and juice to be served. In addition, I also invite any passengers with any questions to speak to me personally during the wait. But when in flight, I do expect phones to be turned off.