Was SSRS installed in SharePoint Integrated Mode?
Did you try looking in the Reporting Services Configuration on the server in question? 

https://social.msdn.microsoft.com/Forums/en-US/a856488b-fbcd-479e-9167-34ddf7ba3e83/how-do-i-find-out-if-ssrs-is-intregrated-or-native?forum=sqlreportingservices