My advice may seem obvious after the fact, and not helpful with your dilemma, but ... when editing a file never overwrite the original; at least until you are completely satisfied with the results of your efforts/experiments. When saving something you have worked on, choose 'Save File As' (giving it an appropriate name such as 'edit 1' or something) instead of 'Save File" (which will overwrite the original.) (I find it extremely helpful to create a folder and keep all files for the project within it)