In this Letter, we reconstruct the formation pathway of MRG-S0851, a massive, logM(*)/M-circle dot = 11.02 +/- 0.04, strongly lensed, red galaxy at z = 1.883 +/- 0.001. While the global photometry and spatially resolved outskirts of MRG-S0851 imply an early formation scenario with a slowly decreasing or constant star formation history, a joint fit of 2D grism spectroscopy and photometry reveals a more complex scenario: MRG-S0851 is likely to be experiencing a centrally concentrated rejuvenation in the inner similar to 1 kpc in the last similar to 100 Myr of evolution. We estimate 0.5 +/- 0.1% of the total stellar mass is formed in this phase. Rejuvenation episodes are suggested to be infrequent for massive galaxies at z similar to 2, but as our analyses indicate, more examples of complex star formation histories may yet be hidden within existing data. By adding an FUV color criterion to the standard U-V/V-J diagnostic-thereby heightening our sensitivity to recent star formation-we show that we can select populations of galaxies with similar spectral energy distributions to that of MRG-S0851, but note that deep follow-up spectroscopic observations and/or spatially resolved analyses are necessary to robustly confirm the rejuvenation of these candidates. Using our criteria with MRG-S0851 as a prototype, we estimate that similar to 1% of massive quiescent galaxies at 1 <z <2 are potentially rejuvenating.