Luzyfuerza:
This story illustrates why I cried for joy when I finally crossed the Nevada border on my move out of the PRK.
Into or out of Nevada? I'm from Vegas - I'm sorry if your gone...
In a nutshell (obviously not intended as legal advice - so don't take it as such
):
The "informant's tip" that the police received may or may not have provided sufficient probable cause for the police to obtain the warrant. It depends. Usually, the Court will look to whether the informant is one that was used before (has a history ratting out people) or has other corrorative indicia of reliability. I think it is safe to assume that your "informant" was only of transient nature (another student with no history giving evidence to police), and therefore, not historically reliable. The police would then have to corroborate the informant with evidence from your posts. Obviously, they didn't have time to look up the posts before they searched the bag.
The pragmatic problem herein, is that the police will most likely get the warrant (or not), search the bag, then find out later that their seizure was unconstitutional under the 4th Amend. Even there, I doubt very seriously that the lower courts, i.e. - the municiple, justice, or district courts in the local and county seats, would overturn the search and seizure. We're talking about elected judges who in some cases are barely out of law school or who have never practiced criminal or constitutional law before. These types of things don't get their fair constitutional consideration until they are looked at by the State Supremes at least. In other words, the police get what they want unless you are willing to take the case all the way baby.
The fact that you didn't give them consent to search the bag was a nice touch. Consent means waiver of your rights. I would not have consented to the search of my body though, either. Police could have done so anyway, but why make their harassment any easier. For the body search, otherwise known as a "stop and frisk", police only need "reasonable suspicion". In other words, not much. An uncorroborated informants tip would have been enough.
There may be claims against the department, school, and informant. I'm not sure what your nationality or ethnic origin is, but depending on your race, etc., your claims might be further legitimized. If you're interested in pursuing it, seek some local legal help from someone who practices in discrimination cases, police brutality, 1983 claims, etc.