TEMPORARY TWR. TKOF WITHOUT CLRNC.

Narrative

IT WAS MY LEG TO FLY FROM KILLEEN ARPT TO DFW. THERE WAS SUPPOSED TO BE AN AIRSHOW ON THE FIELD BUT WASN'T ANY ACTIVITY DUE TO RAIN AND LOW CEILINGS. ATC HAD A TEMPORARY TWR ON THE FIELD THAT WAS NOTAMED ON THE RELEASE; BUT NEITHER THE CAPT OR MYSELF NOTICED IT. WHEN RECEIVING OUR CLRNC; GRAY APCH GAVE US THE USUAL DEP FREQ (118.00) AND WHEN I CALLED THEM BEFORE TKOF THEY SAID CONTACT KILLEEN TWR 118.6 FOR DEP. THE CAPT AND I ASSUMED THIS WAS THE TWR AT FORT HOOD THAT GRAY APCH CTLS. I HAD ANNOUNCED ON CTAF THAT WE WERE TAXIING OUT TO RWY 1; AND AGAIN THAT WE WERE TAKING OFF ON THIS RWY BEFORE TKOF. AFTER TKOF WE CALLED KILLEEN TWR ON 118.6 AND THEY TOLD US THERE WAS A TWR IN EFFECT FOR KILLEEN AND TO CONTACT APCH ON 118.0. WE THEN REALIZED WE HAD TAKEN OFF WITHOUT CLRNC FROM THE TEMPORARY TWR. THERE WASN'T ANY OTHER TFC IN THE AREA DUE TO THE MARGINAL WX. GRAY APCH MAY HAVE ASSUMED THAT WE WERE AWARE OF THE TEMPORARY TWR BECAUSE THERE WAS ANOTHER FLT THAT CAME IN 45 MINS BEFORE US THAT ENDED THEIR DAY AND WENT TO THE HOTEL; WHICH IS WHERE WE HAD JUST COME FROM TO BEGIN OUR DAY. WE ARRIVED THE NIGHT BEFORE AND WERE TOLD TO SWITCH TO ADVISORY FREQ 122.7 BY GRAY APCH AND HAD NO KNOWLEDGE OF THE TEMPORARY TWR THE NEXT DAY.