He did ride a B26 on a bombing run in the SW Pacific. Since he was on a Congressional war committee MacArthur deemed it politically wise to give him a Silver Star.
TOW 9 Mission:
"The Marauders took off from 7 Mile, Port Moresby at 0851 hours. "Heckling Hare", Johnson's aircraft, developed generator problems and was forced to drop its bombs 80 miles short of the target. It returned to base arriving back at Port Moresby at 1008 hours."