The best kept secret of the
2002 Winter Olympics.
On Februrary 4, 2002, canadian icemaker Trent Evans noticed there was no face-off marking on the Salt Lake E-Center arena's ice, he placed a dime to mark the spot. The next day he returned with a Canadian dollar coin and placed the loonie on top of the dime.
Fearing his scheme would be discovered, he covered the coins with a dot of yellow paint, all this while avoiding other (american) maintenance technicians setting up the rink. His secret was kept until the weekend of the Gold Medal men's hockey game between Team USA and Team Canada, where a CBC anchor spilled the beans.
Before that, the canadian women's hockey team was in the know and almost broke the secret when several of them kissed center ice after their gold medal victory against the american team.
Evans dug up the coins after the men's game and presented the loonie to Wayne Gretzky, who has donated it on to the Hockey Hall of Fame in Toronto, Canada.
Trent Evans kept the dime.
Update: The coin may actually be a CAD$2 or twonie, this node will be corrected/renamed in that eventuality.
Canadian Hockey Hall Of Fame confirms it is a $1 Loonie. http://www.hhof.com/html/olypress.shtml