Sounds like they were just looking for reasons to cancel you. Maybe they just didn't need you as a traveler anymore, but unfortunately, I have hear of this happening before...
If they cancel you because they just don't need you anymore, they have to pay financial penalties to your travel company. BUT, if they cancel you because they say your nursing care was inadequate, or because of something they say you did wrong, then they don't have to pay the penalties. It's a horrible, horrible thing for a hospital to do to a traveler, but it's not the first time I have heard of this happening.
Since you have already been canceled, all you can do now is speak with your recruiter/clinical representative from your company. Hopefully if you have a good recruiter & a good company, they will back you up on this, especially if there is not way of proving that you actually did anything wrong. If you have a good recruiter, they should be able to find you another assignment very quickly (within a week), and as long as you're not in some remote rural area, they should be able to find you another assignment relatively close to your current one. If they can't or won't back you up, or can't find you another assignment, contact several different travel companies right away to get to work on finding you something new.
Also, please complete a review of this hospital & share the name of it here so other travelers can avoid having the same thing happen to them. Hospitals that do this to travelers should be boycotted by travelers!!! Once this situation is over, please also fill out a review of your travel company as well, as to how they have handled this situation.
P.S. If you would like the name of a good recruiter with a good company (RN Network), PM me for my recruiter's contact info. I have never been in your situation, but I trust my recruiter enough to know that if I ever was in your situation, he would have my back.