You can attach event to the page to listen for Esc key and then manually trigger the dragend
event.
var ESCAPE_KEYCODE = 27;
var dragEl = $('.draggable').drag(function( ev, dd ){
// do stuff
});
$(document).on('keyup', function(e) {
if (e.keyCode === ESCAPE_KEYCODE) {
$(dragEl).trigger('dragend');
}
});