To edit something with CC HTML Editor you open the file that you uploaded (you should still have it in your 'working' folder on your PC, and that's the one to open). I would not change between code mode and visual mode, since the latter seems to change the code for you each time you open it. Stick to one, and IMO I would go for the code mode...

When you have made your changes you can preview it, but if more changes are necessary you must go back to code mode to add them. Then you save locally and upload again.

If for some reason you have lost the file you were working on (I mean the local copy), you can download it from the web using a FTP client. CC has Direct FTP which costs a few bucks, and Free FTP which is - free.