If you do not know the exact path you may use
git log --all --full-history -- "**/thefile.*"
If you know the path the file was at, you can do this:
git log --all --full-history -- <path-to-file>
This should show a list of commits in all branches which touched that file. Then, you can find the version of the file you want, and display it with…
git show <SHA> -- <path-to-file>
Or restore it into your working copy with:
git checkout <SHA>^ -- <path-to-file>
Note the caret symbol (^), which gets the checkout prior to the one identified, because at the moment of <SHA> commit the file is deleted, we need to look at the previous commit to get the deleted file’s contents