Some really important messages are not showing up in my GMail inbox.

I've found out about them when I go look for them, when I expected an answer from someone and it didn't come. When I search, I find the message. However it's not in the Spam folder. And it's not in the inbox. I can't tell where it got routed to. Just that I had to search to find it.

This is really scaring me. What is going on with GMail?

Also, is there any way to tell how they routed a message? Where it ended up?

PS: Apparently Linus Torvalds has noticed the same thing.