I'm so sorry that Izzy is missing. I wouldn't give up - search you may still find him before you bring a new pup into the house.
Here is a great thread about how to find a lost yorkie
http://www.yorkietalk.com/forums/showthread.php?t=49514
Also, another member has lost a dog & her thread is filled with lots of advice form other members
http://www.yorkietalk.com/forums/sho...hlight=delilah