The 25-year-old actor - who has dated Carey Mulligan and Hilary Duff - is unaware whether the 25-year-old brunette beauty was with her then-fiance 'Beverley Hills, 90210' actor Brian Austin Green at the time of their fling during filming of the movie in 2006.
Asked if Megan and Brian - who married last year after getting engaged in 2006 before splitting in 2009 and reuniting in 2010 - were together during Shia and Megan's fling, the 'Wall Street: Money Never Sleeps' actor said: "I don't know, man. I don't know. I don't know. I don't know. It was what it was."
He added to Details magazine: "Look, you're on the set for six months, with someone who's rooting to be attracted to you, and you're rooting to be attracted to them. I never understood the separation of work and life in that situation.
"But the time I spent with Megan was our own thing, and I think you can see the chemistry onscreen."