Well, you are not calculating in the spirit of the times. Do you honestly believe that in the pre-video era of 1978, Warner Brothers would send a film crew around to capture the sights and sounds of an unproven band on it's first or second tour? This band was lucky enough to eat at McDonalds once or twice a week, let alone get filmed at all in High Def, which didn't even exist back then. Tape recorders (unless purchased at a drug store...so much for fidelity) and primitive video cameras weighed about as much as a Buick, and were hardly fun to lug around, let alone use.
Look at the crap Zep went through with their live DVD from a decade ago. Most of the footage had to be baked (yes, BAKED) in an oven to keep it from falling apart, overdubs were needed, and at one point Jimmy Page sought out bootleggers to contribute footage lost over the years to fill in the gaps.
So yeah, from time to time a small, 5-10 minute bit of footage shows up online, usually culled from hastily (and cheaply) made band promos. Yet to believe there is a WB produced, full feature VH show sitting in the vaults is simply absurd. Besides...Warner would have released it by now, given the financial quagmire that the group has existed in since...oh, I dunno...around the time of that awful VHIII album.
Damned it...a few inches lower and we'd never have heard of Chickenfood...