Not legal - but you probably can't do anything about it.
The whole point of getting a search warrant is that the Constitution requires an impartial judge or magistrate consider the situation and agree with the police that there is probable cause to believe that a crime has been committed, and evidence will be found at the place specified. If the police don't produce the search warrant at the door before starting the search, how does the homeowner know they are telling the truth.
No search warrant is necessary, however, if the homeowner consents to let the police come in and search. NC courts may let the police "stretch" the truth a little and still find that consent was valid. They can't outright lie, however, or the owner at the door can claim that consent was obtained by fraud.
Your problem is that the only person who can object after the fact is the owner or resident of the premises. If you never lived in the house, then you never had a constitutional right of privacy in the house, and you have no standing to object, even if the police search was conducted under fairly egregious conditions.
You might have other grounds to argue that the evidence should be suppressed, but you will probably need to talk to a local attorney about this.