@cjm61 is correct. On multiple item orders, only the first one has the tracking, the others get the red bar. To me, that means that are all shipped together. And if its a one item order, if it gets shipped with something else, it sometimes has the red bar.
But the shipping notices I get in email, you can click on each item to get the tracking info. I now keep track of what is where and what its shipping with by writing down the last 4 numbers of the tracking number, if it's a Z for ups, and the item. Just a quick memo so I don't have to memorize.