...then how does the cop know the warrant even exists?...
How do I know the warrant actually exists?
I am well within my rights to refuse entry without a warrant....and cops are legally allowed to lie....what is preventing any cop form claiming they have a warrant that doesn't exist to gain entry?
Also, at least one actual lawyer disagrees with you
There are two elements that must exist for a search warrant to be issued.
www.notguiltyadams.com
If a cop doesn't have it in their possession, they can fucking come back when they do