Bill G has confirmed that this show did not happen.
Listing: Los Angeles Free Press, December 20, 1974, p. 19
Expost: [contra] "Odds and Ends," Dead Relix 2, 1 (January-February 1975), p. 21. Jerry Moore and/or Les Kippel and/or Harvey Lubar reported shows on two days, 28th and 29th, not this night.
Shows were originally scheduled for December 25th (Christmas!), 26th and 27th, as displayed on a promotional brochure for the December out-of-town gigs put together by Round Records. See "Business: RX-102 – Compliments of Garcia," Grateful Dead Archive, Special Collections, University of California Santa Cruz, MS.332.Ser. 2, box 17, folder 10.