The 29-year-old claimed silver in his pet event, the high bar, at Birmingham Arena on Tuesday.
Bull, who finished fifth at the Tokyo Olympics, initially bombed out in Birmingham, finishing 13th in qualifying due to a poor landing.
Jesse Moore was originally due to compete alongside Mitchell Morgans, but was forced to pull out with a shoulder injury.
Mason Stephens, the next eligible qualifier, was the next man in line. Then, he withdrew, handing Bull a reprieve.
“Clay Stephens having the biggest heart in the world, (it was) just such a selfless act for him to offer that spot to give me a chance on my pet event,” Bull told reporters.
“The message (about Moore’s withdrawal) came through and obviously, it was the big elephant in the room. I gave Clay all the space he needed.
“It was a huge decision he had to make and there was no wrong decision.
“I was never going to ask for the spot because I knew he deserved it and how much hard work he put into earning that as well.
“It speaks to that decision he had to make and the kind of guy he is.”
Despite struggling with a serious ankle injury, Bull nailed his landing to score 14.233, with Cyprus’ Ilias Georgiou (14.466) and Marios Georgiou (14.133) claiming gold and bronze respectively.
“I don’t know how to feel right now,” Bull said.
“Up until last night, my mind was completely off the high bar final. I only trained it a little bit yesterday just to warm up.
“But outside of that I hadn’t done anything since Friday. It was the smallest chance possible that I was even going to be in this final.
“… There’s no chance I was making the same mistake twice. I was gonna put it on my feet no matter how much it hurt.”