Gideon would have showed up with Heath and brought Cassius along as his band mate promised. The zebra got into the alcohol a little bit, but that's nothing new. He generally had a good time, drank some, and danced with a couple of people. Plus, he went out of his way to flirt with Tonks.
When everyone started leaving because of the ministry commotion, Gideon would be standing there along with Heath with WTF expressions.