It seems there's a slight clog in Mass Effect 2's Cerberus Network DLC pipeline. Though the promised bonus mission is still available, the deadly, rugged and elaborately scarred mercenary Zaeed has been held up until tomorrow or Thursday on the Xbox 360, according to a BioWare spokesman writing on the company's official forums.
You could spend time being sad about the delay or you could spend time playing Mass Effect 2. We think the choice should be pretty clear. Just pretend his space luggage got lost or something.