How does a search warrant work?

If drugs were found in your vehicle, law enforcement had probable cause to seek a search warrant on your residence. You should have been given a list of things they removed from your home. Yes, it is a legal search. Letting other people use your vehicle is not a very good idea for many reasons, but you, as the vehicles owner, are responsible for what is found in it. Perhaps your best option would be to seek counsel with an attorney.