I didn't hear the show. However . . .
It may well be that the answer isn't known to anyone. The thing started off on the Fesshole Twitter feed (where people can aanonymously confess to anything) yesterday morning, with many people taking guesses at which song it might be. In particular, Stuart Maconie posted on the thread, promising to invite his listeners to come up with their suggestions as to what it might be:
https://twitter.com/fesshole/status/1639921393440632833
I suspect that Zoe Ball was just keeping the debate alive, rather than actually solving the mystery.