We apply the method of "coherence observation by interference noise" (COIN) to molecular wave packet interferometry. In contrast to conventional wave packet interferometry, where one has to control precisely the relative phase between the pair of time-delayed laser pulses, COIN employs a sequence of randomly phased laser pulses. Whereas in this case the mean signal does not reflect anymore the coherent evolution of a localized wave packet, the fluctuations around this mean still mimic the dynamics of the propagating wave packet. We demonstrate the feasibility of wave packet interferometry without phase-locking by simulating fluorescence interferograms for the Na-2-molecule.