UPDATE 2018: The plugin listed below no longer works with WP (as of version 4.5 I believe) but the code listed in the accepted answer DOES still work, so use that instead.
UPDATE: just found this plugin which does what I wanted and more: https://wordpress.org/plugins/b09-link-to-existing-content/faq
I'm pulling my hair out with this, it seems so simple, but there is no easy way in WP (that I can find), and no plugin that will do the following:
In a post, I want to select some text, and then add a link to an existing (full size) image in my media library. I DON'T want to insert an image into my post.
The only way I have found to be able to do this is to find the image, copy the file link, then go to insert/edit url and paste it in. There should be a way to find it the same way you find pages or posts to link to in that same dialog. (OR maybe there is, and I simply can't find it because I am an idiot.)