The onetime couple were spotted leaving the Hollywood Roosevelt hotel together early Friday morning in Ronson's black Porsche, ending up at her place.
"Watching grey's anatomy – my fav show," the DJ, 33, wrote around 5 a.m. "@lindsaylohan sleeping next 2 me – should i wake her up to let her know her mom is going on GMA?"
But Lohan wants everyone to know her late night outing did not include clubbing at Teddy's, which is attached to the hotel.
"I was just at roosevelt to meet Samantha and say happy birthday to a friend," the recently rehabbed actress Tweeted Friday afternoon.
"I take my sobriety seriously," Lohan continued. "Please dont believe this (sic) accusations. i know the rules and i wouldnt risk probation. xoxo L."
Just last month, Lohan, 24, and Ronson dined at Joe's in Venice, Calif., where a source says they "shared a friendly dinner."