Miley Cyrus' mystery man -- the guy she partied with last night and drove home with in her Porsche Cayenne -- is a boy named Paul Khoury, from her gang of friends.

Could Paul be Miley's revenge date after reports fiance Liam Hemsworth hooked up with January Jones surfaced earlier this week? Or was last night's outing just two friends, innocently hanging out ... without Liam?

We know Paul went to Palm Springs with Miley and Liam and a gaggle of friends last September but we haven't spotted the New Jersey native with Mr. and Mrs. Cyrus in our own archive of X17 pix.

And of course you'd expect Miley to address the whole thing on Twitter, 'cause you KNOW she's seen our story and our photos today. And she did! Well, we think she did ... kinda ...

    “Your soul can fly outward stringed to your ribcage like a shimmering kite in the shape of an open hand.” - JEFF BUCKLEY


Meanwhile, Liam's in Australia, having jetted off to his home country a couple weeks ago to give Miley some breathing room, according to

"Miley is still upset with Liam. She took off the ring to make him mad," a source tells the mag. BUT, "It doesn't mean that they have split. Miley says they are still together."