If a person has no evidence, the locksmith will verify it before leaving. If they don't present the verification, they can close and close the door. Then call the police and let them work it out. There are several ways in which a locksmith can verify ownership of a property.
For example, they can request that the person who contacted them provide them with a recent utility bill for the address they're calling from. This is a way to create a more concrete case that the person who called them is actually the person who owns the house. Without evidence like this, it can be extremely difficult for anyone to prove that they own a specific home. Fortunately, locksmiths will always request this type of verification before deciding to continue.
In most states of the U.S. In the U.S., a locksmith or locksmith company does not legally need to verify ownership or rights to property. That said, if a locksmith company doesn't verify your identity, it's a red flag that they are now an uncertified and even unqualified locksmith.