If you restore your computer to factory conditions (and not a simple system restore to a few weeks ago) everything will be gone and you'll have to reenter the password for internet (wireless, I assume?) access.
Next time write the password down in at least 2 locations.
ETA: I think there are apps available that will read your hidden passwords and reveal them.
EATA: You might want to try this:
Asterisks Password Viewer