Your comments

The link that I am talking about had expired when you looked at it, but not when I gave it to Mr. imgur. None of the ones I've been trying to pull had expired either, as the amount of time you have before it expires is significant/based on views (?).

If that had been the case though, I'd still get the same message because imgur didn't (but does not) accept the URL in the first place. Thanks for the input though!