["I work at a milk plant and today my coworker left early on me. He's always leaving me with tons of work to do!", 'Oh I bet that is frustrating!  Can you report it to someone?', "I have a team leader who I can try to report it to but he always seems to brush me off. It's getting old at this point!"]
I would feel the same way.  Perhaps you could mention it to your co-worker nicely and they will take pity on you.
My coworker left early on me today and left me with a ton of work. I can't believe he always gets away with it.