It’s unfortunate that you lost your work on CodePen. However, you should really be using your own editor so that you can upload your progress to GitHub. Many employers will look to your Git account to see how often you have been coding and for how long. Most students do not learn about the importance of making a strong Git presence on the web until many months after they start learning to code. And by that time, they have lost out on the ability to showcase months worth of their work - Git keeps track of how often you add new code to your ‘repository’ on a public calendar in your profile.
Any of these editors will work great for you:
Atom - used by the Git community
Brackets - focused on web design
Sublime - very popular for general use
Once you have your code working in your editor, you can upload it to CodePen to get it checked.