I do too. I've been wondering if there's some short JavaScript I could add to retrieve text from local storage when loaded, and update local storage after every change. Not so it persists for months, but just so it survives a tab close or a browser restart.
EDIT: mm, localStorage API is disabled inside data URLs, understandably
There are local-first file based solutions (like classic TiddlyWiki) that could work for you,.. but at that point maybe you meant to open your favorite text editor or IDE.
I kind of like that this simple solution always opens a scratch buffer and I have to put it somewhere else to save it (never saved accidentally).
It also keeps the source formatting (or with ctrl-shift-V ignores it), which can be useful aside from the note taking itself.