You could try the following

Get hold of a hex editor (google search for Neo should come up with an excellent freebie)

There are many things you can do with a hex editor but it's ability to search incredibly quickly across huge amounts of data for patterns is enormously useful.

If you can remember a phrase or something that might have been in the notepad file there is a tiny chance that you might find it somewhere on the disk. If you do you might then be able to copy it elsewhere (the free one doesn't allow it but you would at least know if it is recoverable)