The game was broadcast by ABC on May 10, 1973, from the Los Angeles Forum. The Knicks were leading the Lakers, three games to one, in the third finals between the teams in four seasons. The 7:30 p.m. start time was perfect out West, but the potential number of Knicks fans who stayed in front of their television sets until the final buzzer was almost certainly reduced by the 10:30 start on WABC-TV/Channel 7.

When the game ended — a 102-93 Knicks victory — the video seemed to vanish.

No one — no fan nor anyone at ABC Sports — came forward with a tape, as Bing Crosby’s family did three years ago to say that he had stored a kinescope of Game 7 of the 1960 World Series in his dry, cool wine cellar.

“No one could explain where it was,” said Ken Mattucci, the director for content, licensing and acquisitions at MSG Network. “It was the holy grail.”

Last year, as Mattucci started planning for the anniversary, he contacted a collector he knew and asked if the collector had Game 5. He did. Mattucci, who would not identify the collector but said he was prominent in the field of sports video, does not know how the collector acquired the tapes or if he got them from a person who recorded the game when it was first broadcast.

But there was a glitch: the game had been recorded, somewhere in the New York area, in the little-known Cartrivision format — which preceded VHS and Betamax — and only a Cartrivision system could play its 6 ½-by-7 ¼-inch tapes.