The Japanese sent out 12 recce planes to search for the US carriers, one on each segment of a clock face. 1 plane had an engine malfunction and was therefore late setting off - the one that was heading straight to the USN. It finally detected 2 of the carriers, but it's radio failed, so it could not report their position until it got back to it's own fleet, by which time the Americans were attacking.
As for the American planes, the decisive dive bomber squadronn failed to find the Japanese and was at the point of turning back when they spotted a Japanese destroyer going at high speed. They played a hunch that it was trying to catch up with the main strike force so turned along it's course, and sure enough a few minutes later the fatal 5 minutes that destroyed three Japanese carriers were enacted.