It’s fairly common to find how-to’s that show you how to use .htaccess to block hotlinked images, but it seems a lot of them show you to redirect to an outside file. Not sure why that’s a good idea, or not mentioned, but meh.
Now, the important rules are in the second and last lines. The last line redirects any hotlinked images (which don’t come from your sites' domains. The second line un-blocks the redirect protection for only that image.
The five or six different howtos I tried to use this afternoon didn’t include this salient point 🙁