A pet mouse loose in a house survives by being small, silent, and close to walls, and it is usually found by patience rather than pursuit. Grabbing, chasing, and hauling furniture around are the three ways escaped mice get injured or driven deeper into hiding, so the whole approach is built the opposite way: seal a space, read the signs, and let a trap on the mouse's own route do the catching while you check it often.
Seal and Search One Room at a Time
Start in the room where the mouse escaped or where droppings were last seen. Close the door, push a rolled towel hard against the gap underneath, and take other pets out, because a hunting cat or an excited dog changes a shy mouse into a bolted one. Search at floor level with a flashlight, moving slowly along the skirting, behind appliances, under sofas, inside the folds of soft furnishings, and through any box or bag the mouse could have climbed into.
Move nothing heavy by dragging it. A sofa or appliance shifted blindly can crush a mouse sheltering underneath or behind it, so lift, tilt, and look with a second pair of hands where you can, and check inside hollow furniture bases before anything is moved at all. If the room is clear, seal it and move to the next, working outward from the escape point rather than wandering the whole house, and listen in silence for a minute in each room, since rustling in a quiet house carries surprisingly far.
Set the Trap on the Travel Line, Not in Open Floor
Mice travel along edges, not across open rooms, and droppings reveal the route: a scatter of droppings along one wall, behind the refrigerator, or beside a pipe run is the mouse telling you where it walks at night. Place a humane live-catch trap tight against that wall, or build a bucket trap with a ramp leading up to a tilting bridge over a deep, smooth-sided bucket lined with soft bedding. Bait either trap with a small amount of a favorite food the mouse already knows, and put a little bedding from the home cage inside, so the trap smells like safety rather than machinery.
Check every few hours, and always before bed and first thing in the morning, because a trapped mouse waiting all night without water becomes a welfare problem of your making. Refresh the bait if it dries out, and if droppings move to a new wall, move the trap to match rather than adding traps everywhere. An escaped mouse is often caught within a night or two once the trap sits on the right line.
Transfer Without Grabbing, Then Fix the Escape Route
When the trap holds the mouse, keep voices down and resist the urge to reach in. Tip a live trap gently so the mouse walks out into a secure carrier with bedding, food, and water, or lift the bucket, cover it, and pour the mouse slowly into the carrier at floor level inside a sealed room. A frightened mouse can bite, leap, and injure itself against a hand, while a tipped transfer removes hands from the process entirely.
Back in the home cage, watch for limping, labored breathing, or a mouse that will not eat, and call a vet if anything looks wrong rather than assuming a night loose explains it. Then find the escape route before the mouse teaches you about it twice: a lid that flexes, a bar gap at a corner, a door left resting open during cleaning. For a report from next door, that contact matters: nearby owners hear about the escape through the Lost Pet Alert System in KinsLe, and whoever finds the mouse can reach you by direct message rather than handling it alone.