I am so very sorry your Yorkie is missing, and I pray that he will be returned safely.
I know you are doing everything possible to find him, and it is heartbreaking. There is a section in the Yorkie Talk Library that gives endless suggestions to help find a lost dog, and I'll post the link here in case it might be helpful to you in some way.
http://www.yorkietalk.com/forums/mis...st-yorkie.html
Please update whenever you can, and we will all be praying that he is home soon.