A GLF4 flight crew experienced a loss of contact with ATC when both radios were inadvertently selected to the destination ATIS resulting in loss of the Center frequency. Reporter suspects the inadvertent selection was made when he exited the flight deck and the COMM selector switch was activated by accidental contact with the seatbelt.

Narrative

I decided to visit the lavatory and retrieve a refreshing beverage. Upon my return I sat down on the right seat and proceeded to have a short conversation with my co-worker. During the conversation; I tuned COMM 1 to the destination ATIS. A few minutes later; we heard the ATIS being broadcast in our headsets. Puzzled; we looked down at the radios and to our amazement; we had two radios set to COMM 2. I then transmitted in the blind on 121.5; stating our position and altitude; in order to obtain the correct center frequency. Once I contacted the appropriate frequency; the remainder of the trip was completed without any complication. We figured the COMM selector switch had been accidentally activated by a seat belt upon exiting and re-entering the flight deck. I also overlooked this while I was setting the ATIS & company frequency on COMM 1. As a result; the Center's frequency was eliminated from the radio; thus accounting for 'the lost frequency'. Care should be taken when exiting from the pilot's seats. Since the radios are located within inches from each seat; the seat belt can easily reach the function keys of the radios causing an undesirable input/command.