In order to exhume the buried signatures of ``missing planetary caustics in the KMTNet data, we conducted a systematic anomaly search to the residuals from point-source point-lens fits, based on a modified version of the KMTNet EventFinder algorithm. This search reveals the lowest mass-ratio planetary caustic to date in the microlensing event OGLE-2019-BLG-1053, for which the planetary signal had not been noticed before. The planetary system has a planet-host mass ratio of $q = (1.25 pm 0.13) times 10^{-5}$. A Bayesian analysis yields estimates of the mass of the host star, $M_{rm host} = 0.61_{-0.24}^{+0.29}~M_odot$, the mass of its planet, $M_{rm planet} = 2.48_{-0.98}^{+1.19}~M_{oplus}$, the projected planet-host separation, $a_perp = 3.4_{-0.5}^{+0.5}$ au, and the lens distance of $D_{rm L} = 6.8_{-0.9}^{+0.6}$ kpc. The discovery of this very low mass-ratio planet illustrates the utility of our method and opens a new window for a large and homogeneous sample to study the microlensing planet-host mass-ratio function down to $q sim 10^{-5}$.
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