I'm sorry this happened to you, it sucks to not get credit for your work. I think the explanation is simpler though. There is no incentive to say either good

I'm sorry this happened to you, it sucks to not get credit for your work. I think the explanation is simpler though. There is no incentive to say either good things or bad things about a Vendor, the incentive is to keep the focus on the internal people that were involved, because recognizing internal employees is critical for morale and general team cohesion. Recognizing a Vendor's effort could potentially backfire and lead to bad blood internally (happens with consultants all the time) and is not really a priority because the engagement is based on a negotiated contract that is primarily driven by financial or expertise reasons, not the human elements. The fact is, the Vendor is the one that should be worried about the morale of their own employees. The Vendor's management should be praising the good work of the employees, and if there is blatant disrespect coming down from the Company, it is their job to either address it or at least justify to appease their rank and file.