Apart from that its the polite thing to do Tex.
Thunderstruck, I'm not sure what these missing threads are.
We don't delete spoliers as a rule. As mentioned, it would be edited to indicate it is a spoiler.
It may have been merged. If a thread was soft deleted, Admin can see it. I can't see anywhere. It takes extra effort to hard delete it so that's unlikely.
In summary, its a mystery to me. I can look up the Mod logs but that's extra work which takes time. If it is important enough, I'll do that.