I did find the botnet golem eventually. It was on the one planet I hadn't scouted yet essentially.
I had two more questions that came up to me!
Firstly, barracks, is it worth going out to kill them (especially on high mark planets?). I lost my last game because I popped a mark 4 barrack, but I'm also really worried about what happens if they build up.
Secondly, dire guardian lairs. After losing to barracks, this thing wiped me out when I popped it. Do the guardians they spawn scale with AIP, or get progressively tougher? It's another case of wondering how late can you wait before dealing with them.
Lastly, warp jammers, can you put one in your home system? I'm playing a game with tons of counterattack posts, and would love to prevent the waves from hitting my home base, but that's a huge knowledge investment when I'm not sure if it'll even be placable there.