From everything I've read, they never did play as a quartet in those years...from the time of Jeremy's disappearance til Peter Green re-joined to finish that tour, the shows were cancelled/postponed.
COULD they have played San Bernardino BEFORE Jeremy went on his bookstore hike the day of their Whiskey-A-Go-Go gig?
Actually, again from everything I've read, from the time Danny joined the band in '68 until those two or three private party shows Fleetwood Mac did somewhere in the timeframe of 1991/92 as the quartet of Mick, John, Billy Burnette & Rick Vito, they never played live as a quartet.
If anyone has any confirming proof they did do some quartet shows then, please step forward.