TWO PERSONS, NEITHER RATED AS PLTS, TOOK THE ACFT WITHOUT THE KNOWLEDGE OR CONSENT OF THE OPERATOR OR ARPT OFFICIALS. THEY TOOK OFF AT NIGHT, & AFTER A SHORT TIME, RETURNED TO THE ARPT TO LAND. DURING AN ATTEMPTED LANDING, THE ACFT TOUCHED DOWN HARD, BOUNCED TWICE, THEN DEPARTED TOWARD THE SOUTHWEST. A SHORT TIME LATER, THE ACFT CRASHED ABOUT 3 MI WEST NORTHWEST OF THE ARPT, BUT IT WAS NOT FND UNTIL LATE ON THE MORNING OF 4/20/85. IMPACT OCCURRED NEAR A HIGH TENSION POWER LINE WHILE AT HIGH SPEED IN A NOSE LOW, SLIGHTLY RIGHT WING LOW ATTITUDE & ON A HDG OF 140 DEG. AN INVESTIGATION REVEALED THAT THE ACFT DID NOT COLLIDE WITH THE WIRES. BOTH OCCUPANTS HAD BEEN EMPLOYED BY THE OPERATOR AS LINE BOYS. ONE WAS STILL EMPLOYED & HAD ACCESS TO THE OFFICE. BOTH HAD BEEN DRINKING BEER FOR SOME TIME PRIOR TO THE FLT. TOX SHECKS SHOWED THE L FRONT SEAT OCCUPANT HAD AN ALCOHOL LVL OF 0.239%; THE R FRONT OCCUPANT HAD A LVL OF 0.184%.NEITHER OCCUPANT HAD USED THE AVAILABLE SEAT BELT OR SHOULDER HARNESS.