Upon searching through Minneapolis' property info website, new information regarding the 'lost' renovation has come to light. Namely, that it was actually two separate occurrences.
Building Permit 524099, issued 9/13/83, called for the installation of a ticket booth & snack stand combo. It was cleared on 7/3/85, so it's pretty safe to say that the bizarre lobby design was created shortly thereafter. Then, on 5/10/93, Permit 597847 was issued to replace loose and deteriorated brick on the northwest corner of the building (this was cleared almost immediately on 6/18/93). This would be part of the renovation alluded to on the minneapolismn.gov site and a 1991 movie theater rehabilitation guidelines document:
"During the 1990s, the owners acquired the plans from the 1939 renovation and restored the lobby and the second floor lounge areas. In addition, the auditorium’s side walls are adorned with re-created carved murals of Acousti-Celotex." (from minneapolismn.gov)
"The Uptown is presently undergoing an extensive renovation...the owners have acquired the plans from the 1939 renovation of the interior and are restoring the marquee and recreating the Art Moderne and Neo-Baroque design elements of the lobby and second floor lounge areas." (from Neighborhood Movie Theater Thematic District: Guidelines for Rehabilitation, July 1991)
So, then, the mural recreation took place at this time. Because it didn't involve the lobby renovation, the theater likely never had to close its doors, hence why the Star Tribune didn't find it worth writing about. Mysteries solved, except for why the murals switched auditorium walls. The world may never know.
On a sort-of related note, the sales history of the Uptown was also discovered through this search. Lagoon Enterprises sold the area to Uptown Properties on 3/1/83 for $300,000, and then Cann LLC sold to Lagoon Partners LLC on 12/10/09 for $1,399,999. The more you know...
Looks like the 80s renovation can be pinpointed to 1984:
When [Michael] Bender walked into the theater last fall, he was appalled. For too many years, bad management had let things slide to such an extent that the Uptown had become a pigsty. Smoking and drinking at shows was standard, giving the theater an earthy bar-charm that clashed with what was on the screen. The bathrooms were unusable. Kids snuck in. It was a mess, he says...
Bender and Landmark Theaters, which owns the theater, decided to do a little bit of construction. The result, though not quite finished, is impressive. With a healthy splash of lime paint, a few dozen feet of neon tubing and a lot of mirrored glass, the Uptown Theater has been transformed into a veritable art deco palace. The result has been a quieter, cleaner crowd. (from Twin Cities Reader, 5.15.84)