Determining previous TFS 2013/2013 Build Process Template

I am looking at previous builds in TFS 2012 using a custom Build Process Template, and while it is easy to determine what template will be used for my Next build, how do I determine what was used on a previous build?  Example:  TeamA builds ProjectA using TemplateA.  Then they say something was not correct, and they switch to a new TemplateB.  I can see TemplateB in their configuration, but need to make changes to TemplateA (it has custom hooks already in place for other things that are needed). How do I determine what TemplateA was?  It is not in any of the ActivityLogs or in their Build Logs.  Just for the sake of argument, assume that there are 100s of build process templates, not easy to determine which was originally used.