I made defense plans. I kept my warrior home (I've never been outside my own culture), and in a position to beat any solo invader back to my capital. I built a single worker and immediately switched to military, I just haven't finished a 2nd unit yet. If I'd left my worker uncovered, he'd be stolen now.
Regardless, its unfixable now. So either you keep your word about "not a war of conquest", or you don't.