What a locksmith must do.
When a locksmith arrives he needs to identify the issue and immediately after that is to request an ID. Off course for the locked out situation. If the client fails to show valid id with the property number the locksmith will have to find another way to identify that the client is actually working, living at that property. A way will be to ask a neighbor if he knows the person locked out.
If this also fails to happen from various reasons a locksmith will not open the door.
While the locksmith is working on opening the door it s a must that the client be present and no exceptions to be made.
There is also ways to verify the identify of a customer with the social media platforms.
Mainly this will be the common cases for most of the situation.