A few years ago, there was a bot that scraped through ebay results and let the users match it to a Numista page. I understand that this isn't possible anymore (or never was?) because of copyright reasons.
But there is a bot that scrapes through Katz and Heritage sales (maybe even more?) and matches it to Numista pages. But I bet there are lots which the bot can't match. I also suppose that these just vanish?
I suggest that the users should get the chance to have a look at these and match it themselves if possible, just like back in the day with the ebay listings. Maybe it couldn't be matched because the coin is simply missing in Numista, then it also helps expanding the catalog.
The same thing could be done to battle the plague of auction results that aren't matched to a year-line or a grade. Because currently there is no nice way to look for such auction entries only.