I suggest that you write a letter to the appropriate individual in the hospital and ask them to send you the money that was improperly withheld from your check. You may also want to consult a lawyer to determine if you were termnated illegally. Based on your description, you have not provided enough information to indicate whether you would have a potential wrongful terminatin claim. You should also file a claim for unemployment compensation. There is not likely much you can do about the trespass warning.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.