The woman from the audience was his partner, and he switched the dollar bill of other person ( the person picked by Simon ).
The bill he returned for the initials was actually the switched bill. The portion of the bill presented for the initials had been cleverly prepared in advance. The audience member chosen by Simon only wrote "JM"; the rest of the writing ( signature ) was already on the bill.
He then tore the bill in exactly the same way as the pre-torn piece he had already given to Sofia. The "JM" section of burnt bill remained in front of Simon. He burnt the rest of part, while the matching torn piece with Sofia fit together perfectly because both pieces had been prepared to match.
Whatever, it was a brilliantly executed trick with excellent misdirection and presentation.
#AGT #AmericasGotTalent #AmericaGotTalent #AidanCorcoran #AidanCorcoranMagic #DollarBillTrick
