I've watched that brief clip of the postal worker, Richard Hopkins, denying the retraction. He doesn't clarify anything, accuses the Washington Post of being wrong and says "You'll find out tomorrow."
Now normally I would give anyone in his apparent position a great deal of rope and try to at least entertain the possibility they were telling the truth. But Project Veritas is involved.
In fact, now that I've dug a little deeper, Project Veritas supposedly has a covert recording made by the Hopkins of the USPS investigators.
So there's an extremely high chance the whole thing is either another Project Veritas fiction from the start, or that it intersects with reality in a few places and Project Veritas has edited a video to deceive, as it is wont to do.
For those who aren't familiar with this organisation, PV puts an extraordinary amount of effort into creating false stories and trying to flog them to "liberal media" and then turning round and saying "Gasp! You bunch of liars printed a false story. Fake news mainstream media!"
The construction of its fake story on Roy Moore was mindblowing. I watched the documentary, about the how the WaPo's fact-checking caught out the person PV was employing to pose as Moore's victim.
Project Veritas: how fake news prize went to rightwing group beloved by Trump
www.theguardian.com/us-news/2017/nov/29/project-veritas-how-fake-news-prize-went-to-rightwing-group-beloved-by-trump
Deliberately misleading videos seem to be a Project Veritas stock in trade.