Will it not move at all in either direction?
in swapping the x/y plugs you've confirmed that the X stepper and associated wiring still works.
try swapping the X/Y limit switches as well and see if that helps.
once you confirm that the X stepper works in the Y hole,
and the stepper still moves when connected to the Y axis when the limit switches are also swapped.
Then plug in everything as you should and try swapping the stepper drivers, (i.e take out the X and the Y stepper drivers and try putting the driver from the Y axis in the X axis circuitry. (which should pull out) and see if the x-axis works then...
(I'm assuming that the stepper drivers are able to be changed on your printer?)