rusty unky
(n) a friend you once had, and who could serve as an uncle to your offspring, but who you haven't seen for a long time and whose whereabouts are unknown
Child: Dad, whatever happened to your friend Hal?
Dad: Last I know he was in Vegas. As far as I'm concerned, he's a rusty unky.
Dad: Last I know he was in Vegas. As far as I'm concerned, he's a rusty unky.