Yorkies can be difficult to potty train. Good job keeping her roaming room limited when you leave for work.
When you are home, keep the pad in close proximity to wherever she spends her time. Make sure you praise and reward with a small treat when she gets it right.
Outdoors: puppies are often distracted outdoors and do not focus on doing their business. She may also be reluctant to pee and poop outdoors. My Max was that way. I really had to encourage him and praise him when he pottied outdoors.
Hiding to poop: Teddy was shy about pooping when he was a pup.
Try pretending like you aren't hovering and watching too closely. Praise profusely when she does it. Let her know how happy you are, as if she just performed the best trick ever.
If she poops while you are away, that might be one of the reasons she is not peeing on the pad consistently. My pups do not like to go near a pad that has poop on it.
If that is part of the problem, that might be a difficult challenge to overcome until she matures and can regulate her poops for before you leave for work, and for when you return. My pad trained boys naturally fell into a rhythm in which they can do their business morning and evening, and when they know the humans will be there to take care of it right away.