"It's a rumor until they actually trot out the proof. I hope to hell they have it -- but until then, it's only a rumor."
A rumor would be like my saying "I heard on the grapevine that Chief has it". This is Chief himself saying he has it.
And he could be lying, or stretching the truth, or whatever. (NOT that I think he is....)
Chief's word is not enough. It's a rumor until he provides unambiguous proof.