How to Survive if Threatened:
Pigs can adapt to wide range of habitats, have a high reproductive rate (two litters of 4-14 piglets a year), and have few natural predators which makes them hard to control. Known predators of wild pigs include black bears, mountain lion, bobcats, coyotes, and owls, all of which are unable to keep pig populations in check.
Maybe you didn't see an actual pig but instead saw where it has been. Pigs leave evidence from rooting, wallows and rubbings as well as from tracks and from creating trails. The tracks of wild pigs are close to those of deer except they have rounded toes. They generally appear more rounded than the tracks of deer as well as being wider than they are long, plus they are shorter than deer tracks of the same width.
Wild pigs are definitely an unfortunate threat to our natural environment and they are just one more potential danger that a hiker can encounter on the trail.