Shawn, let us know if you got this working.
For others, there is a problem with some mail systems that take a look at a .layout file and, realizing it's a zip file, do you the wonderful favor of unzipping it. Thank you not at all. But both Mac and PC have built-in zip capability. Since Shawn was on Mac, to re-zip and make a LayOut document:
In Finder, select the files (things like doc_thumbnail.png, document.xml, documentProperties.xml, references.xml, styleManager.xml and the directories pages and ref).
Right click on this selection, and choose "Compress X Items" where X = # of items you selected. For 10.4 (Tiger), I believe it says "Create Archive" instead. Either way, you now have a file called "Archive.zip"
Rename "Archive.zip" to your original file name .layout (answer yes to "are you sure"), and voila, it's a LayOut document.
Barry