@Akos4 This one has come up many times before. With most damage/theft claims, Airbnb is totally capricious, but their record is pretty solid when it comes to reimbursing you for changed locks. The complications come up mostly with hosts who have bought too hard into the "trust and safety" rhetoric, which is just marketing. It's never wise to wait for a customer-service subcontractor to help you through a safety issue on the ground - they're not trained for this, they have no time to dedicate to your case, and nothing that could possibly help you is within their power. So when you have an emergency, take the appropriate action first and deal with the bureaucracy later. If you feel your safety is at risk, obviously you call the police rather than your listing service.
When your keys have gone missing, here's the procedure:
1. Immediately safeguard the property and contact your guest to notify them that they will be charged the full cost of changing the locks if the keys are not directly returned within, say, 2 hours.
2. If the issue is not resolved when the specified period of time has elapsed, arrange an emergency locksmith (which should be available 24/7 in London) to change your locks, and be sure to collect the full receipt.
3. Immediately (i.e. before checking in any new guests) send your guest a Resolution Request for the full cost of the locksmith. If they don't accept the charge within 72 hours, advance your case to Airbnb along with the invoice for the locksmith.
4. At some point within 14 days of checkout, leave an honest review saying what happened when your keys went missing (I don't recommend saying they were "stolen" without proof of intent - that would be tantamount to libel).
In most cases, if you've done everything correctly, you'll be paid out either from the guest's payment method or from the Host Guarantee. Honestly, this is one of the only things it's actually good for. But if you need a listing service that also offers criminal investigations and emotional support, you're definitely on the wrong platform. Those are premium services.