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We have discovered spectacular vast molecular gas reservoirs extending tens of kpc outside of two high-redshift post-starburst galaxies as part of an ongoing ALMA CO survey of such objects. While the host galaxies are only 3-5kpc in size comma nearly half the total CO luminosity in each system extends 25-45kpc from the hosts. This discovery was unexpected and both the scale and magnitude of the extended gas features are unprecedented at any redshift. The origin of the vast CO is unclear comma but may be related to AGN outflows comma tidal stripping comma and-or environmental effects. We propose a low-cost comma high-impact VLA+HST campaign to determine the origins of the remarkable gas features and their broader implications for galaxy evolution comma including galactic feedback comma the formation of extended stellar halos comma and metal enrichment of the circumgalactic medium. The VLA data are designed to characterize the presence and effects of AGN - existing data cannot even rule out radio-loud AGN activity - while the HST data are needed to discover stellar tidal debris and-or close merging companions. Together these datasets can uniquely determine the origin of the incredible molecular gas features we have found and place this unexpected discovery in broader context.