Instead of loading the .html in text format, as the name TextEdit implied, it rendered the .html file.
Then I did something incredibly stupid. I went to "Format" and "Make Plain Text" and "OK" to "Convert this document to plain text". After that, it ask me:
"Are you sure you want to modify the document in place?" With 3 options
Overwrite, Cancel, Duplicate.
I choose "Cancel".
Here is the kicker. It changed my .html file into .rtf. (I think it should have been named .wtf). It didn't even ask me to save. Is there any chance that I can recover my original .html file?