Ask HN: Do registrars sell searches?

I've been searching for a particular address frequently over the past couple of weeks on what I consider to be a reputable registrar and to my surprise the primary domain I've been considering was snapped up 3 days ago by a squatter.

Does anyone have any insight into this, ways to avoid it? If it wasn't my registar who looked at my search and sold it, who could it have been? It seems too much of a coincidence.