Liability insurance covers the cost of replacing third-party keys if you lose or misplace them, so that's keys for a property that belongs to someone else.
Covered by the policy:
master/main keys for a central locking system
house and apartment door keys incl. garage, cellar, postbox and adjoining room keys
hotel room keys
safe and locker keys
car keys (incl. rented vehicles)
bike keys
furniture keys
workplace keys
code cards for electronic locks
If the third party (for example your landlord) needs to change the locks for security reasons as a result of the lost keys, this is also covered.
The cost of a locksmith breaking into the apartment, if you lose or misplace your keys, is, unfortunately, not covered by liability insurance.