Well, I finally figured out how to find pictures which were deleted (type Status:Deleted in the search bar), which was very necessary for me as I was approaching the 80,000 cap on how many pics I'm allowed to save to my favorites.
Turns out, even if the pic is deleted from the site, it still gets recorded in your favorites regardless. And I found out I had roughly 64 pages worth of deleted favorites that I had to clear up. With each page able to hold up to 75 images, that was over 4,000 bright white thumbnails I had to click 'unfavorite' on.
It would have made things much faster / easier, if there was some kind of 'mass selection' option for situations like this, where you need to clear up a bunch of images at once, instead of going through them individually one by one.
Updated by Donovan DMC