This has been happening to me more often lately.
I found this:
Saying your code is saved every time you run it in the IDE, which has been my experience previously.
I’m using Chrome on Win 10 64, and lately it has been losing my changes. I run the code to save it every time. I just lost my changes for the puzzle of the week. I absolutely ran it and checked the output after modifying, before closing the window.
Any other info I can give?