B757-200 LANDS WITHOUT CLRNC.

Narrative

WE WERE CLRED FOR AN APCH TO RWY 25L AND THEN APCH CHANGED US TO RWY 19L. WE WERE ON A GOOD HDG FOR A L DOGLEG TO RWY 19L. APCH CLRED US FOR A VISUAL AFTER CALLING THE FIELD IN SIGHT. I WAS NOT FAMILIAR WITH LAS BUT ACQUIRED THE RWY WITH THE CAPT'S HELP AND CONTINUED THE APCH ROLLING OUT ON FINAL ABOUT 2 MI AND SLIGHTLY HIGH. I NOTICED A RED BLINKING LIGHT ON THE RWY CTRLINE IN LINE WITH THE REIL AND ASKED THE CAPT WHAT IT WAS. HE DIDN'T KNOW OR THOUGHT IT MIGHT BE A CAR OR TRUCK. ABOUT THE SAME TIME I WAS BEGINNING TO GET CONCERNED AND WAS CONSIDERING GOING AROUND; THE LIGHT STARTED TO MOVE TO THE R AND AWAY FROM THE RWY. I ASSUMED IT WAS A VEHICLE (TRUCK OR VAN) SVCING THE LIGHTING SYS. I DID NOT NOTICE ANY WINGTIP LIGHTS. TWR LATER TOLD THE CAPT IT WAS A STUDENT PLT IN A LIGHT PLANE. DURING THE SHORT TIME ALL THIS TRANSPIRED; I ASKED THE CAPT IF WE WERE CLRED TO LAND. I REMEMBERED HIS CALLING THE LNDG CHK COMPLETE BUT I WASN'T SURE ABOUT WHETHER APCH HAD GIVEN US A LNDG CLRNC OR JUST SENT US TO TWR. HE TRIED SEVERAL TIMES TO GET THE TWR; BUT WAS NOT ABLE TO GET A REPLY. I ASSUMED WE HAD BEEN CLRED TO LAND AT THIS POINT AS THE RWY WAS CLR AND WE HAD TALKED TO SOMEONE (TWR OR APCH) ABOUT LNDG. THE LNDG WAS UNEVENTFUL; BUT WE DID HAVE TROUBLE GETTING GND CTL. WE HAD HAD A STUCK MIKE ALSO EARLIER ON THAT SAME RADIO. (NOTE: WE HAD NO APCH PLATES FOR RWY 19L; NO MISSED APCH PROC; AND THERE WERE SIMULTANEOUS TKOFS AND LNDGS ON RWYS 25.) (THE CAPT TALKED WITH TWR BY TELEPHONE FROM OPS.) (IN MY JUDGEMENT; I FELT THAT LNDG WOULD BE SAFER THAN GOING AROUND.)