He may or may not have been the first to post about Silk Road on Bitcointalk, or anywhere for that matter, but that seems awfully thin ground for getting a warrant.
I'm surprised HN seems to be in favor of such action.
...things add up and produce enough cause to get a warrant. Given the analysis from opsec people, it's not surprising that there was eventually a warrant and an arrest and a trial; given that he was leaking so much information about who he was and what he was doing, the surprising thing is that the feds didn't catch him even sooner.
He made the post looking for a developer 9 months later, on October 11, 2011.
And as I mentioned below, the fake ID issue seems to have come up after the email warrant was issued, so it wasn't a factor there.
which was apparently the first mention. So, as far as the agent could tell, this was the first person to mention Silk Road on the open Internet. That's what's reasonable.
(Also, from a pure Bayesian POV, the fact that it nailed DPR on the very first try goes a lot towards demonstrating its relevance. NB: this parenthetical is not a legal argument; otherwise you could justify any search that turns up evidence.)
Anyway, my answer was that if the police really had such strong suspicion of someone and they were right, they've got to have enough to get a warrant anyway, which is similar to what you're saying.
The fake ID thing seems to have occurred after the warrant was issued, so I'm not sure I see its relevance.