I worked around the Corona bug in the following manner:
I put all of the HTML and support files (CSS, PNG, etc.) into a folder and .zip’d it.
I put this Help.zip into the (project) ResourceDirectory root
At app initialization (first run), I copy the .zip file to the DocumentsDirectory, uncompress it, and then delete the .zip from the DocumentsDirectory.
In the lua code, I refer my webview calls to “Help/filename.HTML” in the DocumentsDirectory
This works in Simulator and all devices.