How to know if penalized?

A couple of days ago my site was de-indexed for all the words we had ranked except for 1.
Today one of the keywords is back at a much worse position, this seems like a penalty, however, competitors seem to be affected as well, not as hard as us though.
Should we be worried?

There were Google updates which affected everyone in rankings. This is for a short period though, until the things settle up.
If not, try updating your keywords and content.