In my state, Nevada, the standard for concealed is not "discernible by ordinary observation" which is a little grey as to exactly what that means. However this is also an open carry state, so if it's observable it's ok anyway. I personally have only been concerned about printing or revealing my pistol once, and it was just the other day while trying on shoes. Even though it would have been ok legally, no need for anyone in the store to know or getting asked to leave if its against store policy.
IIRC Florida changed their CCW laws(last year or the year before last I think) to make accidental display ok. Not sure if that meant printing was considered an issue before that or not.