So, you booked via priceline on Jan 4 and just found on the void reservation on the day of departure. I think you'll need to provide some context on the timing of the following events.
When did the charge appear on your credit card
When did they send out the email about cancellation
Was there a refund on your credit card (and when)
If the above happened quickly following the Jan 4 date then I think you won't have much luck going after priceline/credit card company. However if you didn't get a refund yet then there's some ground for argument.