First: Retrace Your Steps
Before you assume the worst, spend 30 minutes retracing your day. Call the last places you visited — restaurants, gyms, and offices usually have a lost-and-found box. Check your car (between the seats, under the floor mats). Check coat pockets you haven't worn today. Ask anyone who was with you.
If you had a keychain with something identifiable, post in local Facebook groups or the Nextdoor app. A surprising number of lost keys get returned this way, especially in smaller Dutch and German cities.
If you're currently locked out, see our guide on what to do when you're locked out — getting inside is the first priority.
Call a Locksmith
If you can't find the keys and you're locked out, a locksmith will get you inside. Expect to pay €80–€150 during business hours in the Netherlands, €80–€200 in Germany. Weekends and evenings are more expensive.
Ask the locksmith to let you in non-destructively if possible. Many modern euro-profile cylinders can be opened without drilling, which saves you the cost of a new cylinder. But if drilling is required, you'll need a replacement anyway — which brings us to the real question.
Should You Change the Locks?
This is the part people skip, and it's the most important question. If your keys are truly lost — not just misplaced at home — someone else might have them. The question is: can they figure out where you live?
If your keys were on a ring with your car key (and your car was parked at your home address), the answer is yes. If you had any form of ID, a parking card, or a gym fob with your address linked, the answer is probably yes. If the keys were just loose keys with nothing identifying, the risk is lower but not zero.
The safe move: change the cylinder. It costs €50–€100 for a decent SKG 2 or 3-star cylinder in the Netherlands, or a VdS-certified one in Germany. If you had a locksmith drill the old one, you need a new cylinder anyway. For a rental, contact your landlord — they may cover the cost or handle it for you.
The Smart Lock Alternative
Here's the thing about lost keys: even after you change the locks, you still have physical keys that you can lose again. The fundamental problem hasn't changed — you're carrying a small metal object that grants unlimited access to your home, and if you lose it, you're back to square one.
A smart lock eliminates this cycle. Your phone becomes your primary key. You can also use a PIN code on a keypad, a fingerprint, or an NFC tag. Even if you lose your phone, you can log in from another device and revoke access, or use a PIN code as a backup. The physical key still exists but becomes a rarely-used emergency fallback.
This isn't just about convenience. It's a genuine security upgrade. With physical keys, you have no idea who has copies. With a smart lock, you have a complete access log — you know exactly who opened your door and when.
Nuki Specifically
Nuki's Universal Cylinder is particularly relevant here. Instead of buying a replacement cylinder and then adding a smart lock on top, the Universal Cylinder replaces your old lock and adds smart features in a single install. You're solving the immediate problem (your old cylinder with lost keys) and the permanent problem (relying on physical keys) in one step.
The install takes about 15 minutes. You remove the old cylinder, insert the Nuki Universal Cylinder, and pair it with the app. From that point, your phone, fingerprint, or PIN code is your primary access method. If you ever want to go back, swapping in a traditional cylinder takes 5 minutes.
The activity log gives you something physical keys never could: complete visibility. You can see every time your door was opened, by whom, and revoke access instantly if needed.