[Solved] w2ui table rows not displaying data.

Try using jQuery 2.2.4 or below.

w2ui is not compatible with the higher versions of jQuery.

SharePoint Designer: What does a workflow lookup returns when the item is not found?

Item not found returns: ?????

Unassigned workflow variable returns: ****

Note: If you will look for ID of an item that does not exists then the variable will be assigned to 0.