Start from why this cat is a flight risk
A cat living temporarily with you while her owner is deployed is not settled the way a lifelong resident is. She is in unfamiliar rooms, with unfamiliar smells, missing the person she trusts most, and that unease makes an open front door far more tempting — not out of naughtiness, but because bolting can feel like heading home. Proofing here is less about hardware and more about never giving her an unguarded opening during the few minutes a delivery puts your hallway, your attention, and the street in one straight line.
Create a closed-room buffer before any door opens
Pick one interior room — a bedroom or bathroom away from the entrance — and make it her delivery-time base, with water, a litter box, a scratching surface, and bedding that carries her own scent. When the bell rings or a courier knocks, move her into that room first and close the door fully before you touch the front door. Check the latch with a push, because a door that looks shut but rests on its frame is exactly the kind a determined cat shoulders open. Only once she is behind that closed door do you receive the parcel, and you reverse the order afterwards: front door shut and latched, then her room opened again.
Make the doorstep work for you, not the courier's schedule
Put a polite, specific sign at eye level on the front door: a cat is staying here, please set parcels down and step back, and the door will open in a moment. Most couriers are happy to leave a package on the step once they know why you are slow, and that removes the pressure to hold a door wide while signing a device or taking a heavy box with both hands. If a delivery genuinely needs two hands, bring it in in stages with the door closed between trips rather than wedging it open. Keep hallway shoes, bags, and parcel piles from forming a launch pad or hiding spot right beside the door, where a cat can crouch unseen until the gap appears.
Brief everyone who might answer the door
A temporary-care home often has partners, older children, cleaners, or friends letting themselves in, and your routine fails the first time someone else answers casually. Walk each of them through the closed-room sequence and agree that nobody opens the front door on a shout of 'just a second' while the cat is loose in the hall. Note the routine somewhere visible near the door, keep the owner's and a vet's contact details with it, and make sure her collar and identification are on even indoors during this unsettled period, so that if the worst happens she is identifiable within minutes, not days.
If she does slip out during a delivery
Do not chase her down the street, which usually drives a frightened temporary resident further from a home she barely knows. Note the exact direction she went, leave the door she exited by slightly open with familiar-smelling bedding nearby if the area is safe, and search the immediate hiding places — under cars, in side passages, behind bins — quietly and low to the ground. Contact the owner through the agreed channel promptly and honestly, and alert neighbours on that street the same hour, while she is still likely to be close. A cat new to an area tends to hide near where she escaped rather than roam. Your calm, immediate search matters more than speed. KinsLe's Care Pass keeps this cat's routine, temperament notes, and key contacts in one temporary handover while her owner is away, so the escape plan you act on is the plan her owner prepared, not one you invent under pressure.