HEADING TRACK DEV BY A B737-300 FLT CREW WHEN THEY LOSE COM FREQ WITH APCH CTLR AT ORD; IL.

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WE WERE ON A 160 DEG HDG ON L BASE FOR ILS RWY 9R ORD. I WAS PF. WE COULD SEE ORD AND RWY 9R IN GOOD VFR WX. WAITING FOR TURN TO FINAL; THE CAPT COMMENTED ON SHIFT CHANGE AT APCH AND I AGREED TO NEW VOICES ON COM #1. WHEN WE HEARD NO COMMANDS AT NORMAL TURN ON TO FINAL; WE BOTH COMMENTED ON THAT HE IS PROBABLY KEEPING US SQUARED OFF FOR THE CLOSENESS TO ACFT WE WERE FOLLOWING. NEXT I SAID; WE ARE GOING TO GO THROUGH THE LOC. CAPT AGREED. WE GO THROUGH THE LOC AND STILL NO CALL. THE CAPT STARTS LOOKING AT COM #1 FOR FREQ AND REALIZES WE ARE ON WRONG FREQ. HE DIALS IN A NEW FREQ (LAST APCH FREQ WE HAD). WHEN HE CALLS IN; APCH CTLR DOES NOT ANSWER. I ASKED CAPT SHOULD WE TURN TOWARDS THE RWY. WE BOTH AGREE TO START TURNING CONSIDERING WE ARE HEADING FOR RWY 4R APCH TFC AT ORD AND TO MIDWAY ARPT. CAPT CALLS AGAIN TO APCH CTLR AND GETS THE ANSWER 'WHERE ARE YOU ACFT X?' CAPT TELLS HIM AND IS TOLD TO CONTACT ANOTHER FREQ WHICH HE DOES. WE ARE STILL IN THE TURN TOWARDS RWY 9R LOC AND THE ARPT. NEW FREQ AND CAPT CALLS AND GETS CONTACT AND INSTRUCTIONS TO TURN R HEADING 270 DEGS. LATER WE GET CLB INSTRUCTIONS TO 5000 FT AND WE ARE BEING VECTORED BACK FOR ANOTHER APCH TO RWY 9R. WE ALSO GET INSTRUCTED TO CALL APCH ON THE GND. WE DO AND THEY CALL IT A 'NON EVENT;' JUST WANT TO KNOW WHAT HAPPENED WITH THE FREQ SWAP AND WHY WE TURNED TOWARDS THE RWY OF OUR HEADING 160 DEGS. THE CAPT EXPLAINS OUR CONCERN WITH TFC ON APCH ON RWY 4R AND THEY UNDERSTAND OUR MOVE. SUPPLEMENTAL INFO FROM ACN 582818: WX WAS CLR; RWY AND AIRPLANE AHEAD WERE ALSO IN SIGHT. BY THE TIME WE REESTABLISHED CONTACT WITH ATC; THEY HAD TAKEN US OUT OF THE FLOW FOR RWY 9R AND ASKED US TO MAKE A R TURN BACK TO THE W. THE LOST COM WAS CAUSED BY THE COM XFER SWITCH BEING BUMPED OR SNAGGED BY THE SEAT BELT STRAP AND XFERRING TO THE RWY 9R TWR FREQ SOMETIME AFTER THE TURN TO A 160 DEG HDG.