Not sure if it's turned up yet but it happened and aired on this date. Talk about it here.

Yes, it exists on NJPW Classics 74 and it's complete.   I have it and will get it posted tomorrow

1980-08-22
NJPW
Bob Backlund (c) vs Antonio Inoki
WWF Heavyweight Title Match
Shinagawa Prince Hotel Gold Hall, Tokyo, Japan
Card
★★

This was a real mixed bag. They spent the first 10 minutes of the match not doing much at all, just the generic things you would expect from a Backlund/Inoki match without anything unique. Other points had some real awkward spots, with a terribly contrived collision spot that comes to mind, as well as a botched Enziguri from Inoki that completely missed its mark but Backlund sold it anyway. Finally the finish was really weak. I think that it was supposed to be a countout win by Inoki. Cagematch has other ideas but that had to be it. They were brawling to the outside and Inoki, seeing Hansen and Larry Sharpe making their way to the ring, dived back in, then the bell rang. 
However, there were some minor snippets of excellence that raised this up somewhat. While I wasn’t a fan of Inoki on offense here or Backlund’s selling, the reverse of both was pretty good. Backlund, around the midway point, hit a Butterfly Suplex on Inoki that flung him halfway across the ring. He followed this up with what might be, and I don’t believe this is hyperbole, the greatest Piledriver of all time. This looked like it killed Inoki and the crowd believed it too. What I loved is the lengths Inoki went to sell the damage this caused him. For a solid 2-3 minutes all he was concerned with was his head and neck. He rolled to the outside, he gathered himself, he even headbutted the ringpost to shake the cobwebs away. From that point onwards every subsequent move that Backlund hit, or teased to hit even, the crowd were fearful as Inoki was vulnerable, more vulnerable than I recall ever seeing him before. And for that 5 minute stretch, this was really excellent.