What if he already had his hand on the throttle to slow down from seventy to fifty, the projectile hits and he is stunned or injured. Wouldn't it be possible for him to unintentionally push the throttle forward then snap out of it and that's when the break was applied. If he was injured could he of been coherent enough to talk to another about the projectile, but out of it enough not to realize he was pushing the throttle forward?
They already said the injury he has isn't consistent with being hit by a projectile.