B737-300. AFTER TKOF FLC BEGAN FLYING SID AS THEY NORMALLY DO; BUT CTLR INTERVENED AND TOLD THEM THEIR CLRNC WAS TO FLY AN ASSIGNED HDG AFTER TKOF. FLC FO HAD RECEIVED THE CLRNC BUT EITHER FORGOT TO TELL THE CAPT AND OR BOTH PLTS FORGOT DUE TO LONG WAIT FOR TKOF. RPTR CAPT SAYS THAT IT WOULD HELP IF TWR WOULD REITERATE THE AFTER TKOF HDG IF IT IS DIFFERENT FROM THE SID.

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DURING CLBOUT FROM LAS ON THE MEAD 1 SID; TURNED TO HDG OF 100-110 DEGS TO PROCEED TO BLD (116.7 MHZ) VOR; AS PER SID INSTRUCTIONS DEPARTING ON RWY 1R AND AFTER PASSING 4000 FT. DEP INQUIRED AS TO OUR HDG; WE REPLIED 110 DEGS DIRECT TO BLD. DEP INSTRUCTED US TO IMMEDIATELY TURN BACK TO HDG 060 DEGS (AS ASSIGNED?). WE REPLIED THAT WE HAD NOT BEEN GIVEN ANY HDG ASSIGNED BY PREVIOUS CTLR (TWR); THAT WE WERE PROCEEDING VIA THE SID. HE SAID THAT 060 DEG HDG WAS GIVEN TO US DURING CLRNC DELIVERY. WE REPLIED THAT WE DIDN'T RECEIVE THAT DURING CLRNC. HE SAID HE'D CHK PAPERWORK. NOTHING MORE WAS SAID. HE GAVE US 145 DEGS TO INTERCEPT THE BLD 111 DEG RADIAL; KARLO ARR TO PHX; AND THEN SENT US OFF TO ZLA. IN COCKPIT COMS SHORTLY AFTERWARDS; IT WAS DISCOVERED THAT COPLT DID RECEIVE THE CLRNC OF 060 DEG HDG FROM CLRNC DELIVERY; BUT EITHER FORGOT TO MENTION IT TO CAPT (ME) OR I JUST DIDN'T HEAR IT. NEVERTHELESS; WE REALIZED THE SCREW UP AND TALKED ABOUT HOW IT COULD BE AVOIDED IN FUTURE. EPILOGUE: THERE WAS A LONG (30+) MIN TAXI DELAY AT LAS PRIOR TO DEP DUE TO SINGLE RWY ARRS AND DEPS. THERE WERE APPARENTLY NUMEROUS MEAD 1 DEPS THAT FLOW CTL WAS TRYING TO SPACE OUT BY 'WEAVING IN' OTHER DEP DIRECTIONS DURING TAXI OUT; CAUSING MORE OF A DELAY. IT WOULD PROBABLY HELP IF THE TWR WOULD REITERATE THE HDG TO FLY AFTER DEP TO 'KEY' US IN TO MAINTAINING BETTER DEP AWARENESS; BECAUSE WE GET SO ACCUSTOMED TO JUST FLYING THE DEPICTED SID OUT OF LAS. THAT WOULD ELIMINATE ANY QUESTION IN WHAT TO FLY; EVEN IF A CREW WERE TO FORGET INSTRUCTIONS GIVEN 30+ MINS EARLIER. DURING A TAXI EXERCISE LIKE THE ONE AT LAS THAT MORNING; YOU BECOME MORE CONCERNED ABOUT SEQUENCING AND RWY/TXWY INCURSIONS; SINCE THERE HAVE BEEN SOME SERIOUS ONES IN THE PAST; THAT YOU GET SOMEWHAT DISTRACTED.