Liam was chillin' at a bar and restaurant in Byron Bay, where he's been hangin' since his split with Miley Cyrus was made public.

Seems like Liam's the only one who hasn't hooked up since the split. Miley's been with Kaitlynn Carter, Brody Jenner's ex. Brody's been with Josie Canseco, and then there's Liam. Don't get us wrong ... he has options.

Miley released a song a few days ago, essentially saying what we reported last week ... her team says she was frustrated Liam was abusing substances, including booze and pills -- something his side strongly denies. His side claims the breakup is all about Miley's behavior. His side claims she hooked up with Kaitlynn before the split ... her side says they split months ago.