Palpatine feigned to Mace to convert Anakin. He had something Anakin wanted. If Yoda could not defeat him, Mace certainly could not in a real battle where the dark lord uses his full strength. Palps says to Yoda, "Now you will experience the full power of the dark side". Yoda goes into hiding, because he realizes that he will not get another chance at defeating Palps and that he must live to fight another day, which he did thru Luke.