Go to terminal and enter
updatedb
This updates the database the following will look through.

Click
Enter the name of the file you are searching for. Pick where to do the
search. In this case "File system". If it is something "you" put in your own
directory area you would pick that. This is not that situation.
Click at the bottom left of the window.

If the file you are looking for has been on your system for sometime the
updatedb command would not be needed. It was done here to make sure the
database is up to date.