He was just seen in the dub in the Ookido's lab episode. [spoil]And you'll see him again soon enough as he's used in Satoshi's battle with Kogome.[/spoil]
Of course he didn't release it.Why would he release a powerful pokemon?Well it is now at Oaks Lab.[SPOIL]Ash uses Snorlax in his Battle Arena Match recently[/SPOIL] He will still use it in the future,it's never going to be released.