If I met John, I would call my mom.
I know this sentence is a second conditional example, which relates to a hypothetical situation.
But I don't know whether I can also understand it in such a way if the covert context is:
I may have met him, but I am not quite sure about that. My memory can't last that long. The only thing I am sure about is that whenever I meet him, I will call my mom immediately. Thus, if one day I find out I indeed met John before, I will be sure that I called my mom immediately on that occasion.