Shih Tzu need a lot of attention, if you leave him alone too long he'll
get upset with you and will show it. We had one many moons ago, he used
to lift his leg on our indoor plants, he started hiding his food behind my
pillow or the sofa cushions, and he once did his business in the bed of
our dog sitter because she was late walking him.
They're awfully cute, lovable dogs, but don't provoke or annoy them,
they'll get even!
Just spend more time with him, and he'll reward you.