gtcalgary:I Saved as Source Files and looked in the manifest.xsf file for some settings I could alter, and I found some references to older versions of the file
The VSTA project, its C# codebehind files etc, are not stored in Infopath Xsn template (or its source files).
You should have saved and passed with a template the whole VSTA project, the one you csproj file opens.
It is easy to find the VSTA project location if to hover a mouse over a tab of opened (from from that project (when it was opened from Infopath Designer) in VSTA file