Need to delete protected Numbers file, forgot password

What's that Lassie? *woof* A boy forgot his password?! *woof woof* And he can't delete the file?! We must send for help!

About 2 years ago I created a password-protected Numbers spreadsheet. Now I'm cleaning out my hard drive and need to delete said file, but I can't remember the password. It isn't saved in Keychain Access either, much to my chagrin.

Is there any way to delete the file without entering the password, or is it forever trapped in a well?

Warmest regards, happy new year, etc.