If someone in control gives them permission. It does not actually have to be you. This is fact specific and it is unlikely that a trial court would toss any evidence. If she was not charged then it is moot.
I think their main argument would be that if they didn't search the room for the contraband, there was serious jeopardy that the contraband would be destroyed. Also, if they claim they saw someone somehow put evidence into the room, that would be another argument.
The "Patriot Act" has had almost no effect on local law enforcement at all. So, unless this was a search by the FBI involving national security, the Patriot Act is pretty much moot.
Since we don't know who was looking for what and why, there is no way to provide any real perspective.
Second, there are other circumstances that will permit such a search besides consent or a search warrant. Assuming no other exigency exists, you are correct - they will need consent or a warrant.