But there are tens of thousands of people doing this sort of idle search, then later register attempt, all the time.

Even incredibly unlikely coincidences will turn up occasionally (and then trigger blog speculation). Without more evidence, coincidence is still a highly likely explanation here.

Your blog post says that it was registered through GoDaddy. That's not surprising as (last I checked) they are the largest registrar and of the millions of domain names registered a month, it's altogether likely that your domain name was one of the several hundred thousand that were registered through GoDaddy in that three day period.

However, you now claim it was registered by GoDaddy, not through GoDaddy? Your lack of precision in your terminology and the fact that you don't reveal the domain name for anyone to verify isn't helping your case.

It's most of the time coincidence. Especially with GoDaddy being the largest registrar. Millions of customers and two people had the same idea.