The P38 was said to be very very difficult to intercept during a reconaissance flight,and I had read that only the Fw190 TU had a chance to make it.
There is some possibility that either he had been shot at earlier in that flight or was recceeing an area becoming known to the Luftwaffe, who had been succesful intercepting before there..
Having recently been on an enforced no-flying period, he'd also be not well practised. Without his great renown and influence, no doubt he wouldn't have been allowed to fly again, but was definitely committed to facing the enemy head on, so pushed to resume flying.