However, since he was still under contract with Universal Music, the singer songwriter was fired from the ITV show.
On Saturday night, viewers saw BGT boss Simon Cowell telling 19-year-old Ryan: "We have a bit of a problem, and I think you know what that problem is, don't you? You're on another show which you're signed up to.
"You signed a contract with another company so why did you come and audition for this show?"
Ryan replied that "song writing is my thing and I wasn't allowed to express my own music on the other show," and insisted that Britain's Got Talent was "a better opportunity."
As the BGT semi-finalists were whittled down, Simon was forced to tell O'Shaughnessy: "I'll be absolutely blunt with you, we were going to give you a yes, but I can't... you understand that."
The 19-year-old said he understood the decision '100 per cent' but vowed to return - and return he has.
According to the Daily Mail, Ryan has since managed to get out of his contract with Universal and will take his place among this week's hopefuls.
The BGT semi-finals kick off tonight, where nine acts including choir Only Boys Aloud, dancing dog Pudsey with his owner Ashleigh and Where's My Keys, Where's My Phone rapper Zipparah Tafari will be competing for a place in next Saturday's final.