Site reader AceOfSpades informed me that WISH TV ran an interview with Anthony Gonzalez recently where he stated he suffered an injury setback on Tuesday of last week. This setback is most likely the reason he did not participate in mini-camp over the weekend. I contacted WISH TV and they confirmed the story. They are also sending me the video transcript.
So much for Gonzo being "100%."
UPDATE: Gonzo's setback might not be his knee. Jason LaCanfora just Tweeted: "Colts WR Anthony Gonzalez dealing w/minor hammy injury, unrelated to his knee surgery. Should not be out of OTAs long. More at NFL.com"