The west bank never belonged to Jordan.. It was administered   i.e. occupied,  by Jordan  after the 1948  war with Israel.. In fact the Brits and the UN  voted to create an Arab state at they same time that Israel was created..  The Arabs had 20 years from 1948 to 1967   to establish  a   Palestinian state  but they were more interested in trying to destroy Israel than in doing anything positive  for the Palestinians.