This isn't the only place people find out about SN, the Peaceful Pill Handbook is another major source people use to CTB. I doubt anybody would automatically associate SN with this site, unless they happened to have read some of the articles. This site doesn't pop high up in search results for SN, you have to scroll through a few pages to reach it.
The use of SN has been increasing, but it's still relatively rare on the local scale. I live in a city with about 4 million people, and I read the medical examiner's report on deaths. I have yet to see an SN suicide, the majority are guns and hanging. So I expect most people doing investigations may know what SN is at a general level, but they won't know detailed information like how people learn about it.
It's not particularly likely people will find your SaSu posts through internet search, since only a few pages end up in search results. If you posted your real name, or used the same member name you used on other sites like social media, then you might be found through search. The only way to see all of someone's posts in SaSu is to figure out their member name, register for an account, use it enough to activate the search bar, then search for posts by that member.