Today I witnessed someone pull a cell phone from his pocket, decide to ignore the call, and proceed to put it back in said pocket without stopping the vibration.
I had a professor once receive a call during class. The ringer was audible. He took out the cell phone, decided to keep teaching, and put it back...with the ringer still audible.
We really ought to know this. When a cell phone rings and/or vibrates and you wish to ignore it, there is a button on it that will make it stop ringing and/or vibrating. Most phones it doesn't matter the button -- just push any button and it will stop. Easy.