ashtonfluxx230.jpgAshton Kutcher's bud Chris Masterson is denying he was partying with Ashton Kutcher and his alleged mistress Sara Leal at Fluxx nightclub in San Diego ... problem is, Chris is in the photos!

When asked if Masterson saw himself in the photo to the right, he responded, "I don't know, I was home sleeping."

You know what they say ... a picture is worth a thousand words.

Watch the video above to hear how Chris responds when asked if he'd allow Ashton to sleep on his couch if Demi kicks him out of their house.