'Jon & Kate' Kate Spends Birthday Alone As Jon Hangs With Alleged Mistress

Where was her husband Jon?

"I went out to Utah for, like, five days," he says. "I just wanted to get back out there and ride with my friends. It just happened to fall on Kate's birthday."

Not shown on camera: Deanna Hummel, the 23-year-old teacher with whom Jon had a three-month affair. A source confirmed to Us Weekly they were together at a Spring Gruv party at The Canyon in Utah on Kate's March 28 birthday.

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