Indoors, close doors and clear one room at a time with food sounds and treats. Outdoors, search cover near the escape point and move fast: it is a prey animal.
Work out which search you are doing
If your guinea pig lives indoors, it is most likely still in the house. If it got out of an outdoor run, or a door was open, treat this as an urgent outdoor search. A guinea pig is a prey animal and, in the words of the Merck Veterinary Manual, is easily injured outside its cage. In either case, shut cats and dogs away before you do anything else. Vet-reviewed guidance from The Vet Desk starts here as well: close external doors, then close the lower part of any open window so the guinea pig cannot reach the sill.
Searching indoors
Take one room at a time. Check every corner, then under each sofa and bed, behind appliances and curtains, and inside bags and boxes. When a room is clear, shut its door behind you so the search area keeps shrinking. Remember stairs: The Vet Desk notes guinea pigs can climb some stairs and hop down them, so check other floors. Listen for rustling. Then put a favorite treat, such as a strip of bell pepper, in an open place in the room you suspect, and wait quietly where you can see it. Merck says guinea pigs are mostly awake during the day, and The Vet Desk says they are most active at dawn and dusk, so try all of those hours. Move heavy furniture slowly, watching the floor.
Make the sounds that mean dinner
Guinea pigs learn what food sounds like. Pet behavior writers report that many wheek, a loud repeated squeal, at the rustle of a bag or the opening of a fridge door. This is a reported habit, not a guarantee, but it costs nothing. Stand in the middle of each room, rustle the bag, stop and listen. Do it at normal feeding times. If you have a second guinea pig, put its cage in the room you suspect. Merck describes guinea pigs as social animals, and a cage mate may help draw it out, though that is owner experience. A frightened guinea pig may stay silent, so a quiet room does not prove it is empty.
Catch with a towel, not your hands
Do not lunge. The Vet Desk warns a sudden grab can cause panic and injury. Approach calmly, gently place a clean towel over the guinea pig, then gather it up securely, with support under its body. Pet care guides say the darkness under the towel helps calm it. If it has backed into a corner, sit down and let it settle first. If it is running along a wall, use cardboard or a laundry basket to steer it toward a carrier. Stay low to the ground while you lift it, since a fall can hurt it. Put it straight back in the cage and shut the door.
Searching outdoors
Start at the escape point and search slowly: thick shrubs, ground cover, wood piles, under decks and sheds. Go with one helper and stay quiet. Put out a carrier or small hide with hay, vegetables and familiar bedding. Forum keepers report a guinea pig may slip back into a familiar hide if it thinks nobody is watching, so step back and watch from a distance, or use a pet camera as The Vet Desk suggests. Keep checking often, since a prey animal in the open has few defenses against the cats, dogs and birds of prey in your area.
Heat, cold and food set the pace
Merck says guinea pigs are comfortable at about 65 to 75 degrees, and temperatures above about 85 degrees can cause heatstroke, so a hot day makes this urgent. Nobody has good data on how long a lost guinea pig can last outdoors, and we would not trust a number. Food is a second concern. Merck says guinea pigs cannot make their own vitamin C and need it daily, and VCA says a guinea pig that stops eating needs veterinary attention right away. Have one that has been loose for a while checked after you find it. The Association of Exotic Mammal Veterinarians lists vets at aemv.org.
Tell the neighbors
The Vet Desk recommends telling neighbors, with a photo, and asking them to check gardens and outbuildings over the next few days. Children often spot small animals. Call nearby vets, shelters and small animal rescues, since people who find a lost pet often phone them. Post in neighborhood groups, and our post on how to post a lost pet on Facebook and Nextdoor has the wording. Ask specifically about hutches and chicken coops. Ask dog owners to keep dogs leashed for a few days.
How a guinea pig flyer should differ
Your audience is a few streets, not a whole town. Use a two-per-page flyer and hand it door to door rather than hanging posters at big intersections. Write LOST GUINEA PIG, and add a description for people who are unsure: a large tailless rodent, about the size of a small rabbit with short ears. Give color and coat, such as long hair, brown and white. Add: Pet, cannot live outdoors. If you see it, try to cover it with a box or laundry basket and call. That instruction is useful in a way it would not be for a dog, because a stranger can trap a small animal without chasing it. End by asking people to check sheds and under decks tonight.
Sources
The Vet Desk: thevetdesk.com/pet-lifestyle/guinea-pigs/how-to-find-a-lost-guinea-pig. Merck Veterinary Manual, Unique Needs of Guinea Pigs: merckvetmanual.com/all-other-pets/guinea-pigs/special-considerations-for-guinea-pigs. Merck Veterinary Manual, Housing and Nutrition: merckvetmanual.com/exotic-and-laboratory-animals/guinea-pigs/housing-and-nutrition-of-guinea-pigs. VCA: vcahospitals.com/know-your-pet/guinea-pigs-problems. The Guinea Pig Forum: theguineapigforum.co.uk. Guinea pig sounds: info.pangovet.com/pet-behavior/guinea-pigs/guinea-pig-sounds. AEMV: aemv.org.