Hi Jim-
I’m less busy these days now that I’m self employed 
Your information about how LayOut saves files is correct - LayOut works in a temporary folder, and then zips the contents of that folder into a single “.layout” file to save it.
@PlannedSuccess, unfortunately when LayOut tried to save this file for you, something happened during the zip process and the file got truncated - the end of the file is missing. Also unfortunately, one of the missing files is the “references.xml” file that tells LayOut how to connect the various pieces of the document. (@adam I wonder if LayOut could write out references.xml before writing the “refs” folder?)
I was able to repair the zip archive in the following manner:
- Rename it to Elgin.zip
- Run a zip-repair utility on it. Since I’m on Mac, I could use the following command:
zip -FF Elgin.zip --out Fixed.zip - Rename Fixed.zip to Fixed.layout to open it in LayOut (or leave it as a .zip to use an unzip utility to look at the internals of the file)
However, I still haven’t been able to get LayOut to load this file due to the missing references.xml file.
In regards to the large file size, I noticed that you have multiple SketchUp models with basically the same name - I think that perhaps you could make some workflow changes that would dramatically reduce the size of your file, which in turn would make it less likely that you’d run into file corruption issues. I’m not a workflow expert so I don’t have an exact recommendation but do some reading up on the best ways to pull multiple models into a single LayOut file.
I think most of your work could be recovered from this file with about half a day’s work but even then you’d still need to review everything to make sure nothing was missing. Sorry I wasn’t able to be more help.
-Marc