What you should use was a 'point' and an 'orient' constraint.
What I usually do is that I link/place locators at each 'state'
i.e: then hand and the mouth, then 'point' and 'orient' constrain the object to all the locators.
Now you can animate the 'weights' of the constraints to make the object follow/align with the locators.
I have a small example of a guy walking with his sword in his hand, then holding it with his teeth and then back in his hand.