I'm hoping and praying that you are quickly reunited. Poor baby. I hope that someone has taken him in and is looking for you. There have been several happy stories of found yorkies here. I know that one recent story involved a quick listing on Craigslist that was quickly seen by the person who found the dog. Good Luck!!
Here is a sticky that may have some ideas you haven't thought of yet....
http://www.yorkietalk.com/forums/showthread.php?t=49514