I had completed over half the original document with color coding & notes
Your document might not be totally lost but you might be able to recover only the last-saved version of it, assuming that you had not turned off AutoSave. You don’t say what your operating system is, so I will assume it is Windows. Use the Windows Explorer file manager to look for your document, probably in the My Documents folder. The file name may be changed slightly. If you had not already assigned a file name to it, it will have a default name.
Always best to say: What your OS and version is. And what have you already tried.