My order of The Flash - S6 almost had that occur. For several days it had a "We're trying to get this shipped but if it's not by xxx then we'll cancel and refund." The entire time it was available for ordering. It finally shipped 48 hours before that arbitrary deadline.
I'm still waiting for...
The only thing I wanted that I've not been able to get, at least at the more-than-reasonable $9.99 BB price, is the Sylvester McCoy Doctor Who - Season 3 BR set. It was sold out 2-3 weeks ago and has not come back into stock even though it's part of their BF sale. I really expected them to...