Welcome to YT! It sounds like you're doing a pretty good job so far. I believe that your vet should have a scanner that will read the pup's microchip (if he has one)..however, because there are many different types of scanners, you may want to take him to your local SPCA (I'm not sure what it's called in the US) or to another vet as well.
Best of luck to you and Myles!
Yorkies are the BEST and if you wind up keeping him you'll have loads of fun
