Chill dude, I was offering an explanation for the reason why other posters were asking questions and speculating about your game, not accusing you of being a liar.
It is entirely possible to have events not visible in the Event Log, even when in SM-mode because NPR and spoiler actions are only visible there if you've enabled Designer mode. So when playing your first game, it's possible that something is happening under the hood that you're not aware of. For example, the two missiles could have come from another NPR that you hadn't encountered before - it's rare but possible. It's also possible to have spoilers and NPR spawn in the same system, meaning that those two missiles could have come from a Precursor ship. Again, it's rare but possible.
Both entirely possible. I doubt it was the CoA firing from a ship I couldn't see, because I wasn't having any trouble spotting them, even with the low tech sensors I was using, but it could certainly have been another NPC race that I never saw (although why another race would shoot at me is a mystery to me, unless they had a colony in the system too, that I never saw (which I doubt, because I was having no problems spotting CoA populations (including a colony on another planet in the same system, which I didn't know existed until I got the message saying I'd lost contact with it)). Again, unlikely, but possible.
Precursors are an option, obviously, but I doubt it, for the following reasons.
1I already encountered what I now think were precursors in another, nearby system. One of my early explorers was doing a routine geosurvey, when I suddenly got a message that it had been attacked and destroyed. It had spotted 2 ships on active sensors shortly before it was destroyed, and based on the size, I'm going to call them FACs (specifically, the game assigned the name "Sovremenny" to the class, which is good enough for me). I sent my main fleet to investigate. My entire fleet (2 x 12kt DDGs, 2 x 6kt FFGs and 2 x 5kt DEs) was completely wiped out. The only thing we detected was one new class ("Longsword"; we never had any contact other than an EM signal from an active sensor of much longer range AND better resolution than mine (so, either high tech, or very large). That means that I also have no idea how big it is or what it can do, although I'd hazard a guess that it might be the Sovremennys' mothership?). I never had active sensor contact (not that it would have made much difference; it was my first fleet, so the missiles and FCs I had didn't have anything like the range my search sensors did). What I do know is that either Longsword, the 2 Sovremennys, or 1 or more other ships that I never detected re capable of firing 2x9 size 10 missiles about every 2 minutes. Slightly more than the 2 missiles of unknown size about every 30 minutes, no?
Recently, I sent another scout to the same system (the same ship as was attacked by the CoA, in fact), and she spotted the 2 Sovremenny's again, before they destroyed her, too (though she did pick up more EM contacts, this time from the Sovremenny's, and also determine that they can do at least 8k km/s).
Given the ease with which they destroyed my (admittedly terrible) fleet, I don't think that they would have been limited to 2 salvoes of 2 missiles. Of course, this is assuming they were Precursors in the first place, but they destroyed every warship I had (not counting a terrible, outdated monitor that was the first warship I built and which didn't have the endurance to get to the system where the "battle" happened(not that it would have done much to help anyway(at least, it wouldn't have helped me XD))).
Also, It occurs to me that, if there were precursors in the CoA's home system, it's likely that I would never have met the CoA in the first place. While I don't know the spawn chances of Spoiler races, gambler's fallacy also says it's unlikely that 2 groups of Precursors would spawn 2 jumps away from one another, when I haven't met them in any of the other systems I've explored.
Overall, I'm pretty confident that it was the CoA that attacked me.
One final note; I apologise, I know I have a tendency to ramble on about things that are only vaguely related to the original topic. I only hope you're enjoying reading about the antics of a new player who didn't (and, to a (slightly) lesser extent, doesn't) know which end of a nuke is the explodey one