klark0 - 1:17 pm on Oct 12, 2012 (gmt 0)
Yes, you can have a manual penalty and not be notified about it. They stepped up communication with webmasters this year, though. But it's still possible.
I suppose the only way to be sure is to file a reconsideration request. If you got a reply, saying "No Manual Spam Actions - Found", then you're in the clear as far manual penalties go.