Our Moma guinea pig escaped into the vegetable garden some weeks ago. This is an area of about an eigth of an acre with large shrubs and bushes, a hothouse with a jungle of foliage plants, many clumps of herbs and other plants all providing unlimited hiding places. Moma has since had babies - we see them shooting under places we have no hope of catching them from when we go into the garden. Meanwhile we have no vegetables; everything is eaten off by marauding gp's as fast as it grows.
As for bait (depending on the surrounding area) you could try some Alfalfa.. I know mine just love the stuff! Although if there is some growing wild, that may not work. Also depends on where mommy was kept, my GPs go crazy when they hear a plastic bag rattle, they think they are getting treats. That might lure mom from hiding. Other then that, I'm not sure what to do short of chasing them down with fishing nets :)