I know that there's mention of this date in another thread I started here, but I wanted to draw attention to it.

We lost 50% of our traffic on Tuesday, November 20th, 2012, and haven't recovered since. That day I don't believe lines up with a Google Panda algorithm update (which we were hit by and recovered from in the past). I got some confirmation that other forums were hit on the same day as me.

Does anyone know what happened that day? Any feedback appreciated!

The update on that day has been kept a corporate secret.

I did some research on this day Dani and unfortunately nothing was announced by Google - except for the #22 Panda update. I did read somewhere, it may have to do with your hosting server (which seems illogical) and I did hear that those effected recovered. You want to submit your site to Google and see why your ranking was effected.

According to moz.com

http://moz.com/google-algorithm-change

Panda #22 - November 21, 2012: After some mixed signals, Google confirmed the 22nd Panda update, which appears to have been data-only. This came on the heels of a larger, but unnamed update around November 19th.

I think I was hit by that "unnamed" update :(