I've lost my last gong piece!

I sent someone to pick it up at the mosaic and she walked off with it. I minimized the game to check something on a website, and when I came back a few minutes later, the gong wasn't complete and the piece is nowhere to be found! I can't even remember who it was that picked it up =(

What do I do?

Here's what you should do: Simply quit out of the game, then go back and try to get the last gong piece. It should be there

actually, if its the mosaic peice, you have to redo the last part of the puzzle to get it back