Zihba was found to be sick after losing his unbeaten record in the Tattersalls Irish 2,000 Guineas.
The Fozzy Stack-trained colt went into the Curragh Classic on the back of three wins, most latterly in the Amethyst Stakes on his seasonal reappearance.
But he had to settle for eighth of 11 to Romanised, and Stack said: “Zihba actually came back with colic after the race.
“He spent two or three days in a veterinary hospital after it, but he’s home now.
“Obviously he’s having a bit of an easy time, but we can safely draw a line through it.
“It’s a bit of a relief in a way and they didn’t have to operate on him so he’s having a break now before he comes back later in the season.
“There’s plenty of races for him.”