Typically a workflow form will go through multiple process stages for approvals and it might have been either approved or rejected in any of the process stages. The status value of the request might have been reset because of rejection at any of the process stages. Sometimes the user or reviewer might have recalled the request. To track this information, click on the history icon at the bottom of the page and you will know the different status updates at this stage.
To know the detailed history click on Admin -> History. Click here to know more about history.