The couple was en route to the Maldives for a festive vacation in 2011, and Legend planned to pop the question to his longtime partner on the trip.
However, the singer was thrown into a panic when an overzealous employee at the airport almost discovered the engagement ring.
He tells Britain's Glamour magazine, "When I proposed I was excited and a little nervous about doing it right. I spent my time on the ring and I was ready to do it when we went on vacation in the Maldives.
"The most difficult thing was hiding the ring. When we were going through airport security in Sri Lanka, the officials were poking around my bag and almost asked to look inside the box where the ring was, as Chrissy was standing right next to me.
"Luckily, they had a change of heart. Who knows, if they had opened the box then, I'd be telling the story of how I proposed to her in Colombo airport."
The pair is planning to wed in the autumn (13).