And as he examined himself, he could find no scars or signs of injuries from the impact of the bulldozer--if there had ever really been a bulldozer.
He had a broken arm from the impact. 
mnli hypothesis: He had a broken arm from the impact.  premise: And as he examined himself, he could find no scars or signs of injuries from the impact of the bulldozer--if there had ever really been a bulldozer.