"They were touchy-feely and very flirtatious. There was a level of comfort there," the fellow partygoer explains. "You could tell they've hung out a few times."

But Rob better watch out! Dylan's dad keeps a close watch on his model daughter. "Sean has really high standards for his kids," says a friend. "Any guy who dates Dylan should watch his back and treat her right!"

After the show, Rob led Dylan to a waiting car, which whisked them to Chateau Marmont for drinks and french fries. From there, a group headed back to Rob's home in an exclusive gated community. One onlooker exclusively tells Life & Style, "They went into his kitchen, and he put his arms around her. Then he was kissing her neck and talking all lovey-dovey. It was clear they'd been out together before." When fellow guests left at 5 a.m., Dylan was still there.