Oh, you're right! Now I see why so many people are complaining about the 2011 Help. I opened 2011 and clicked F1 for the first time to see if I could pull it from there, and gave up and went back to 2010. Here is the Help from 2010. The only time that I've lost drawings from the Project was due to the disappearance of the drawings corresponding XML file. I had a backup up, so just copied it back in.
"What do I have to consider when working with the XML files in the project?
The project data of a building model is contained in the APJ file, which contains information about the overall project, and in the XML files accompanying each DWG file. Both file types are well-formed XML. In most cases, you should not try to edit these files manually in an XML editor, as you might inadvertently corrupt the file. To make changes to your project, use the Project Browser and Project Navigator commands instead.
NoteDo not delete any XML files generated by the Drawing Management feature. They are vital to the project.
I have added a lot of project details in the Project Browser. Can I export these to another application?
Yes. The project details you enter in the Project Browser are stored in the project’s APJ file, which is a well-formed XML file. If you want to export these details, create a copy of the APJ file, and export it to any XML application or database. If you want to use the project detail categories and items in another project, use the existing APJ file as the template for the new project.
What should I do if my APJ file has been accidentally deleted or corrupted?
Deleting or corrupting the project’s APJ files has no influence on the DWG files and XML files contained in the project. In the Project Browser, the project will not display anymore. To recreate the project with a new APJ file, go to the Project Browser, and create a new project of the same name in the same folder location as the previous APJ file. For instructions, see Creating a New Project. Then, go to the Project Navigator, and drag-and-drop the Elements, Constructs, Views, and Sheets folders of the project from Windows Explorer into the corresponding tabs of the Project Navigator. This re-inserts the files into the project.
What should I do if an XML file has been accidentally deleted or corrupted?
Each DWG file within a project has an accompanying XML file that contains the project-specific information. If the accompanying XML file is accidentally deleted or corrupted, the DWG file is no longer recognized as part of the project and will not display in the Drawing Explorer. To insert it into the project again, convert the DWG file into a project file. For instructions, see Converting a Drawing to a Constructand Converting a Drawing to an Element."