Pull your drivers side front tire (or crawl under and look from behind the tire) and the abs wire should originate from the hub and go up from there. Most of them are attached with a clip to the brake line right behind the brake caliper and then run up from there. It goes thru the steel panel into the engine compartment at some point.

If it's missing entirely then I'd say a replacement would probably go a long way to turning off your three amigos! Stranger things have happened off road than snagging an abs line that should be tucked up out of the way...