CAPT OF AN MLG LANDED AFTER THE TWR ISSUED GAR INSTRUCTIONS DUE TO ANOTHER ACFT ON THE RWY. HOWEVER; THE TWR'S XMISSION WAS BLOCKED BY ANOTHER ACFT CALLING IN AND THE RPTR NEVER HEARD THE GAR. THEY HAD ASSESSED THE ACFT THAT LANDED BEFORE THEM AND NOTED THAT HE WAS CLRING THE RWY AS RPTRS WERE TOUCHING DOWN.

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ON FINAL APCH INTO STL; WE WERE THE THIRD AIRPLANE IN A TIGHT LNDG SEQUENCE. THE AIRPLANE AHEAD OF US WAS DOING S-TURNS ON FINAL FOR SPACING WITH THE AIRPLANE AHEAD OF HIM. WE HAD SLOWED TO OUR FINAL APCH SPD FOR SPACING. THE AIRPLANE AHEAD OF US LANDED AND WAS TURNING OFF THE RWY. WHEN WE WERE AT 100 FT AGL; THE AIRPLANE AHEAD OF US WAS CLR OF THE RWY; THEN WE HEARD A BLOCKED XMISSION FROM AN ACR FLT XXX. WE LANDED UNEVENTFULLY. AFTER LNDG; GND CTL ASKED US TO CALL THE TWR ON THE PHONE. THE CAPT SPOKE WITH THE TWR CTLR AND THE CTLR INFORMED HIM THAT HE HAD ISSUED A 'GAR' TO US. THE CAPT TOLD THE CTLR THAT WE DID NOT HEAR THE XMISSION BECAUSE OF A BLOCKED CALL. THIS COULD HAVE BEEN PREVENTED IF APCH CTL WOULD'VE SPACED THE PLANES WIDER. WE MAY HAVE HEARD THE GAR XMISSION IF THE CTLR WOULD HAVE TRIED AGAIN OVER THE BLOCKED CALL. THE LNDG WAS COMPLETED SAFELY AND THERE WAS NO CONFLICT WITH THE PLANE IN FRONT OF US. SUPPLEMENTAL INFO FROM ACN 420049: IT LOOKED AS IF A GAR MIGHT BE REQUIRED. AS WE CROSSED THE END OF THE RWY; IT APPEARED TO ME THE ACFT AHEAD WOULD CLR THE RWY BEFORE WE TOUCHED DOWN. AS I STARTED MY FLARE; THERE WAS A RADIO XMISSION WHICH WAS TOTALLY UNINTELLIGIBLE AND GARBLED. I FOUND OUT LATER THE TWR CTLR HAD ISSUED GAR INSTRUCTIONS WHICH WERE APPARENTLY BLOCKED BY AN ACFT CHKING IN ON THE FREQ. BY THE TIME WE TOUCHED DOWN THE OTHER ACFT WAS CLR OF THE RWY.