There are many reasons you might miss a period. Simple things such as stress or exercising too much can cause a missed period and many girls are irregular during the first few years of menstruating. But if you've missed a few periods, be sure to see your healthcare provider.
Courts usually find probable cause when there is a reasonable basis for believing that a crime may have been committed (for an arrest) or when evidence of the crime is present in the place to be searched (for a search).
n. sufficient reason based upon known facts to believe a crime has been committed or that certain property is connected with a crime. Probable cause must exist for a law enforcement officer to make an arrest without a warrant, search without a warrant, or seize property in the belief the items were evidence of a crime.