In this paper, we combine the partial linearized density a) Electronic mail: mmondal@ur.rochester.edu b) Electronic mail: todd.krauss@rochester.edu c) Electronic mail: pengfei.huo@rochester.edu matrix (PLDM) approach with a stochastic Lindblad dynamics to simulate polaritonic spectroscopy in lossy cavities. To include the cavity loss dynamics, we develop stochastic Lindbald dynamics, which exactly reproduce the Lindblad dynamics when averaged over an ensemble of trajectories. With this combined approach, we simulate the linear and non-linear spectra of a monomer and dimer coupled to a single-mode cavity. With simulated linear and 2DES spectra of the polariton, we systematically investigated the influence of the light-matter coupling strength and cavity loss rate on the optical signals. In particular, we demonstrate that the polariton coherence (interpreted from the off-diagonal peak of the 2DES spectra) can be significantly prolonged by increasing the light-matter coupling strength, providing a theoretical verification of the polaron decoupling effect. 9