Unlike his Vorta commander, Dasreen, Janek'ajan immediately suspected something was amiss when Gul Berat encouraged Dasreen to go on the rec deck alone with him. The Cardassian's neurological impairment was no cause, in his mind, to abandon all caution--especially since he seemed to be engineering some very suspicious and potentially dangerous circumstances for the Vorta.
Janek'ajan's suspicions were correct: Berat had indeed laid a trap for the Vorta. But before Janek'ajan ever had a chance to confirm what was going on, "Dasreen" summoned the Jem'Hadar to their converted cargo bay for the distribution of the white. The Cardassians vented the atmosphere, killing the Jem'Hadar, including Janek'ajan, and keeping the bodies for study. (Star Trek: Sigils and Unions--"Let He Who Has Eyes See")