A few weeks before the end of December last year, I acquired a new domain name and rebranded one of my biggest sites. (I wouldn't normally consider doing such a thing, but the definitive domain name for my niche was handed to me on a silver platter, and I am happy to report the domain rebranding did not adversely affect my traffic or ranking in my niche.)

As part of the rebranding, I added a mod-rewrite which redirects the old domain name to the new domain name.

It's 6 months later now, but still, on my Adsense daily stats, the old domain name gets 1 hit per day. Not two hits, not three hits, just 1 per day.

What could this be? Even though the domain still hits my server, because of the mod-rewrite it is impossible to end up at a page containing Adsense using that domain. Cached somewhere? But then, wouldn't it be inconsistently a few per day? Why always 1 per day? Even a hole in my mod-rewrite scheme would, one would assume, let people in inconsistently a few per day. But the count in the daily Adsense stats for this old domain is always 1.

Anyone have a clue why this would be happening?