Just found this page on Elliot Mazer:
https://en.wikipedia.org/wiki/Elliot_Mazer
Seems he worked on a number of mixes not currently listed starting in 2002. Was it he who did the unreleased mix of Cheap Thrills? It is listed as (remix-SACD).
He did the 5.1 mix of Cheap Thrills, which is more of an ambient/crowd-in-the-rears affair. I don’t think we know who did the unreleased quad.