MD80 CREW MAY NOT HAVE OBTAINED CLRNC TO LAND.

Narrative

THE CAPT WAS FLYING THE ACFT ON APCH TO DFW ARPT IN VMC CONDITIONS. AFTER LNDG ON RWY 17C BUT BEFORE GIVEN CLRNC TO CROSS RWY 17R; I DIALED IN GND FREQ IN ANTICIPATION OF THE XING. AFTER DOING SO I NOTICED THAT IN THE SELECTED SIDE OF THE COM #1 CTL HEAD WAS FREQ 127.07 (APCH CTL). AT THIS POINT; I WAS UNSURE IF I HAD INADVERTENTLY DIALED IN GND CTL ON THE SELECTED SIDE AND BY HABIT SWITCHED THE SELECTOR (BACK TO APCH CTL FREQ). WE COULD NOT SPECIFICALLY REMEMBER WHETHER WE HAD SWITCHED TO TWR BEFORE LNDG AND BEEN GIVEN LNDG CLRNC. UP TO THIS POINT; NEITHER OF US HAD NOTICED ANYTHING OUT OF THE ORDINARY. WE SWITCHED TO TWR FREQ AND WERE GIVEN CLRNC TO CROSS RWY 17R. NEITHER TWR NOR GND CTL MENTIONED THAT WE HAD NOT GOTTEN LNDG CLRNC OR HAD ANY TROUBLE COMMUNICATING WITH US. WE ARE STILL UNSURE WHETHER WE LANDED ON APCH CTL FREQ WITHOUT LNDG CLRNC OR IF THIS WAS JUST A CONFUSING MISTAKE IN THE WAY I DIALED IN GND FREQ AFTER LNDG. SUPPLEMENTAL INFO FROM ACN 408642: IT APPEARS THAT WE EITHER MISSED THE FREQ CHANGE TO TWR; OR WE WERE NOT GIVEN THE CHANGE. WE PROBABLY DID NOT HEAR OR ACKNOWLEDGE A CLRNC TO LAND. BETTER COCKPIT DISCIPLINE TO VERIFY LNDG CLRNC WOULD HAVE PREVENTED THIS EVENT.