“I’m completely shocked,” Hancock told BBC Radio Guernsey.
“Triple isn’t my first event and I got fourth in the last games, so I was thinking maybe the same again and I was aiming for personal bests, which I did.
“I’m really happy.”
Asante’s gold medal was the third won by Jersey on the opening day of competition in Orkney.
Tom Atkinson won gold in the men’s triathlon with his effort also helping the island’s men secure team gold in the event.