It looked to me like the truck ahead of her struck the board as it was laying in the road... i dont think it actually left his trailer.
I had this exact thing almost happen to me a couple of years ago in a little coupe.
the truck ahead of me struck a bent piece of re-bar laying in the road, it flew up and was headed right for my windshield... a bent corner of it grazed the headlight and it bounced back off to the side.
damage to the headlight was surprisingly minimal.
could have been worse.
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