Pull up the door sill and pull back some carpet. If it was flooded there will be sand/silt If it had been submerged it probably would have wierd elctronic glitches. We recently rebuilt a flood damaged truck, and it was quite obvious what happened to it. I think more likely is that someone either snapped it into 4wd while the tires were spinning, or it was beat up by the previous owners kid. They probably took it to ford and was told "It'll be about 3k to fix, but we would let you trade it in, full blue book on this new one"