GameObject.Find(path) searches the currently loaded scenes for an existing GameObject with a specific name. It does not create a new GameObject using data loaded from a file path.
So, this line would only do something useful if, inside your scene, you had a GameObject named "file://C:/path/to/my/model/file.dae" - then you'd instantiate a copy of that ...
To me it looks like part of the code was simply not executed due to an error. You should get the logs for your build and check if you do not have any error.
You should not assume that because you do not have errors in the editor you will not have any in the build.
You can find the info here : unity logs
The streaming asset path might change ...