All the article says is "bloodied body". So we don't know (unless I missed it re-reading the thread ) whether it hit him full on, in the upper body, or just clipped him in the head.

So maybe, if he'd seen it, all he'd have had to do was thrown himself to the ground. Normal human reaction time is 1/2 to 3/4 of a second. You don't have to register "OMG, there's an airplane coming right at me, I need to run to the side and get out of the way." All you need is "OMG there's something coming right at me!" And we're all pretty good at that basic level of survival response.

Ultimately, though, this was just an unfortunate concatenation of circumstances. Or "Stuff happens."