Would you also admit that since you were mistaken about having a personal relationship with Jesus Christ, the definition of being a Christian, that you were never really a Christian at any point in your life?
To be fair... your question assumes that Jesus Christ exists and that being a Christian means you have a relationship with Him. If you assume that he does NOT exist, then being a Christian just means you THINK you have such a relationship. Steven fit that bill.
He doesn't have to say "I was never really a Christian". It's the OSAS crowd who needs to make that argument to remain sane.
II - You are, however, moving outside the bounds of "invincible ignorance". It may be time for a screen name change.
We could raffle off the rights to pick it?