Did someone cut the cable off or is it just missing because they couldn't get the replacement part?

As far as I can find out you'll need to talk directly with Apple to get the special cable (no part number listed for it). FYI - you can use a regular Thunderbolt cable if you have to (review the guide). Good Luck

Here's the iFixIt guide so you can replace it 27" Thunderbolt display

UPDATE

Here's an image of the cable end the other is mounted directly on the display (not intended to be removable)