Agree with Pub User... you have a radio; don't be scared to use it! There are no such procedures in civvy street - at Heathrow there are often long delays in transmissions on some frequencies and it is not unusual for pilots to sensibly enquire "Are you still there?"
Don't take any action yourself unless you have positively determined that there is a radio failure. If you believe the problem to be at the ATC unit do try another frequency (if one is available) before doing anything too drastic.