How to find computer files
If you can remember the name, search for files with that name.
If you can remember when you last edited the file, check for files edited on that date/ at that time.
Next try searching for every file of that type, and order them by date and look for likely suspects.
Search your memory sticks, search your backups, check your laptop.
Once every other possibility is exhaused, check your desktop.
If you can't remember the name try searching by date of modification.