Brownie, could this be the August 1957 "jam" you are talking about? It's all I see listed with Pres involved for August of that year.
unissued performance, Hollywood Bowl, LA 8/22/57
JATP
Sweets, Pres, Frog, OP, Herb Ellis, Ray Brown, Louis
Bellson, Jimmy Rushing*
Polka Dots and Moonbeams
Blues
Goin' To Chicago*
How High the Moon
Someone to Watch Over Me
I think this is it and here is what it says below:
"This concert was reportedly recorded by Norman Granz;
other tunes may have been played."
Likely NO ONE has this, it hasn't been out on record
according to this (discographic pages of Japanese Pres box).