"They were kissing, they weren't hiding it," an eyewitness whispered to the New York Daily News's Confienti@l blog.
According to the source, Upton met up with Diddy at a Miami club party on March 24, a little more than a month after she and Detroit Tigers pitcher Justin Verlander broke off their relationship around Valentine's Day.
Another source said the duo had dinner on Thursday in New York.
For what it's worth, Upton denied any relationship (or "sucking face") with Diddy, tweeting: "Really??? Not at all true.."
And Diddy issued his own denial, tweeting that he and Upton don't know one another.
Attention all Media. I don't even know Kate Upton personally! I'm not dating her ! What's being reported is not true. END of story!— iamdiddy (@iamdiddy) April 10, 2013