I am soooo glad you found him! It's amazing how fast Yorkies can move! After the scare of 72 hours alone, away from home, Jake may change somewhat on his own. If he will entertain the idea, while the memory is fresh, you might want to be attentive and comforting to him...if not by touching/handling him, certainly with soft warm words and loving gazes in his direction...treats wouldn't hurt either.
Also, say yes to the harness...
I like the step in kind rather than the over-the-head kind. Make sure the harnesses fit properly. Both of my Yorkies were able to step out of one set of harnesses...they can still use them but ONLY under clothes...and the first harness I ever bought was for a Shepherd/Labrador mix, Honey (Houdini), which she stepped out of on the very first use...it went back to the store.
I am anxiously awaiting posts about positive interaction and the winning-over of Jack by you!