selectable.unselect
Fires when an item is unselected.
The callback has one parameter which returns a reference to the unselected item.
selectable.on("selectable.unselect", function(item) {
});
If you require a list of unselected items instead of listening for when each individual item is unselected then listen for the selectable.end event instead as this returns a list of items that were unselected during the current selection.