Regarding the date of 2/2/69 Toronto, ON when Led Zeppelin played The Rock Pile venue with opening act Mary Lou Horner, which is mentioned in this Dec 2007 Toronto Star article here.
Mary Lou Horner was the house band at The Rock Pile venue that played country-rock and also was the support band for other acts such as John Lee Hooker and Chuck Berry.
Canadian songwriter, multi-instrumentalist and producer Ben Mink was the guitarist in the group.
Below is a couple of photos from Ben's website. Photo 1 Photo 2
Ben Mink has performed with lesser known Canadian music acts throughout the 1970's, including a stint with Canadian progressive-rock band FM.
Original founding member of FM; the late Nash The Slash (electric violin, electric mandolin, and vocals), was also in the audience at the Led Zeppelin concert according to this archived post here. Mink replaced Nash in FM later on.
FM also recorded a techno-rock cover version of 'Shapes of Things' by The Yardbirds.
FM also opened for RUSH in the late 70's (Permanent Waves "Semi-tour and some of the Hemispheres" Warm-up Tour) and early 80's (Permanent Waves Proper Tour and Moving Pictures Tour).
Later on Mink collaborated with k.d. lang, and co-wrote the Grammy Award winning song 'Constant Craving'.
Ben was also producer of Heart founder Ann Wilson's 2007 solo album Hope & Glory. Included on the album is a cover of 'Immigrant Song', which charted as "the #9 most podcasted song of 2007" on the PMC Top10's annual countdown.
Then Ben produced Heart's latest two albums Red Velvet Car (2010) and Fanatic (2012).