@meercat23 and @Rhaidimiddim , my family said it. I knew a woman from Yorkshire who knew it, and one of my grandparents was from Yorkshire, so I wonder if it originated from there. I did once start a thread on Chat and people knew it in different forms around the country.
I take it as meaning 'search me, I don't know where he is', like someone at home saying, "Where's Dad?"
De-rail, I know. Guilty, m'lud.