Well, on a drug where you've forgotten the difference between up and down and are now convinced you're able to walk through solid objects, I'm pretty sure you'd forget about being depressed...
He's being downvoted for making a moronic criticism: what the person feels under the influence of ketamine is obviously irrelevant, of no value for treating depression, this would be just as obvious to the researchers as to him, and so they couldn't possibly have meant that, and indeed, the second sentence of the article says benefits last well beyond the immediate influence.
I think it's under-appreciated and find the experience exhilarating.