UNAUTH LNDG. LNDG CLRNC NOT RECEIVED.

Narrative

ARRIVING IAD AT ABOUT XA00 LCL. I WAS PIC AND PNF. WX WAS SCATTERED TO BROKEN CONDITIONS WITH BASES AT ABOUT 3000 FT. WE WERE VECTORED BY APCH CTL FROM THE SW FOR RWY 1L. AT ABOUT 20 MI FROM THE FIELD AND AT ABOUT 6000 FT WE WERE CLRED 'DIRECT AML; RPT FIELD IN SIGHT FOR THE VISUAL.' VISIBILITY WAS GOOD TO THE E BUT LOUSY TO THE N AND NE. WE WERE STEPPED DOWN TO 2000 FT ALL THE WHILE LOOKING FOR THE FIELD. FINALLY AT ABOUT 4 DME WE CAUGHT SIGHT OF THE FIELD'S LIGHTS AND THE RWY; RPTED THE FIELD INSIGHT AND WERE CLRED FOR THE VISUAL APCH. WE DID A 'SLAM-DUNK;' LINED UP ON THE RWY AND WERE IN THE SLOT AT 500 FT. TURNING OFF THE RWY I NOTICED THAT I HAD NOT DIALED IN THE GND FREQ WHICH IS MY USUAL HABIT AFTER I CONTACT TWR. FO CALLED GND AND RECEIVED CLRNC TO THE RAMP. LATER THAT NIGHT AT THE HOTEL I COULDN'T GET OVER THE IMPRESSION THAT WE HAD NEVER CONTACTED TWR AND RECEIVED CLRNC TO LAND. I QUESTIONED THE FO THE NEXT DAY AND HE FELT WE HAD BEEN CLRED TO LAND ON THE APCH CTL FREQ. I AM STILL UNSURE WHETHER WE WERE EVER CLRED TO LAND. I BELIEVE THE MAJOR CAUSE OF THIS CONFUSION WAS THE FATIGUE AT THE END OF A LONG DAY; UNEXPECTEDLY POORER VISIBILITY THAN RPTED OR EXPECTED; AND THE HIGH WORKLOAD OF THE CLOSE-IN 'SLAM-DUNK' APCH. ALSO ARRIVING AT THE ARPT AT A 45 DEG ANGLE TO THE RWY AT NIGHT; LOW ALT; IN POOR VISIBILITY MAKES PICKING UP THE ARPT MUCH MORE DIFFICULT AND DISTRACTING.