How can I get spotlight to search everywhere for any file?

Spotlight doesn't search hidden & system areas at all, by design.

The simplest way to get around this is to use something like EasyFind (freeware) instead. You might need to allow it access to Photos Library, in Privacy and Security preferences.

It doesn't index, so it's slower than Spotlight, but it will find anything, anywhere.

There are two things that may cause this issue.

1. Some locations / folders are excluded as mentioned by Tetsujin's answer. In addition to that answer, check your System Preferences > Spotlight and see if the file in question is not excluded in the tabs Search Results and Privacy.

2. In my experience the Spotlight index goes bad relatively often for some reason. Try rebuilding it using one of these methods:

   a. Use an app like Onyx

   b. Follow the method recommended by Apple

   c. Issue the following commands in the terminal (most thorough method, only for experienced users):

   mdutil -i off /
   sudo rm -rf /.Spotlight-V100
   sudo rm -rf /.Spotlight-V200
   mdutil -i on /
   mdutil -E /