person A: I recently discovered that a coworker's decision have led to me having a big increase in my workload - it was super disappointing!
person B: I am very sorry! That is very frustrating! Can you speak with a supervisor about the situation?
person A: Yes_comma_ it was frustrating.  Our supervisor is pretty uninvolved_comma_ but I might need to speak with him to prevent this from happening again.
person B: I don't blame you_comma_ I would talk to him. Even if he is uninvolved_comma_ it is not fair for you to bear the full weight of the tasks at hand. I sure hope he has a solution and the work load eases!