i found mine outside. someone said they saw her before i got her like a month before. depending how cold its gotten their is still hope. my caramilk NEVER left the bush she was living in. they can claim small areas like a bush or hole as their area and not venture from under cover. Theirs a chance wild animals have gotten them if your neighbors have cats they let loose or foxes in the area but dont give up hope just yet. venture father away in a circular pattern from where you think they got out. Did they react to pellet feeding time with wheaks? shaking a containing of pellets as you search may help. Also have you asked around to the neighbors? Fliers and a $20 reward. hand them out in the area. especially let kids in the area know. they go everywhere and most would like $20 in their pocket.. adults wont care and are too busy with work and home life to look for wild animals they dont stumble upon.
Dont lose all hope. guinea pigs naturally rummage in the under foliage in jungles. they're incredibly hard to find. they first instinct to noise or vibrations is to run into their hiding spot and be quiet.... pellets might change that behavior and have them come out of their hiding holes.