I recently inadvertantly clicked someething that has now deleted one of my contacts & "blocked" anything in future from her – I need her email address – how can I retreive it?

I recently by mistake clicked something that has deleted one of my contacts & blocked all future emails from her - don't know how I did this except that I was trying to reduce the size of the screen ( which I still haven't managed) I need that e m address & would like to know how I can reverse my error please? Thanks