After finding Pawel's paper. I seriously doubt Gavin knew the guy from the start or atleast when Satoshi left.
Check this
I quote Gavin from WSJ
I think hes an academic, maybe a post-doc, maybe a professor who just doesnt want the attention, said Gavin Andresen in an interview at his one-man office in Amherst, Mass., last month. And thats why hes proven anonymous.
wsj.com/moneybeat/2014/03/06/bitcoin-foundations-andresen-on-working-with-satoshi-nakamoto/