This paper addresses the problem of identifying whether a given pattern of unobservable events has occurred in a partially observable timed discrete event system. The systems that are considered here are modelled with safe labeled time Petri nets. To solve the problem, we propose to use a model checking approach. Given the model of the system, the pattern to analyse, and the sequence of observations produced by the system, the method firstly builds automatically a labeled time Petri net and a pair of queries that represent the pattern diagnosis problem to solve. The second step then consists in using a model-checker for time Petri net that provides the answer to the queries. The solution provided by the modelchecker is then analysed to determine whether the pattern under investigation has definitely occurred or not.