Update: Sources with knowledge of the matter told All Things D that Cheyer left Apple in June to pursue other projects.
The publication cites three people familiar with the situation, each confirming that Cheyer is no longer working at Apple. The engineer was most recently attached to the iPhone maker's mobile software division and marks the second such departure from a former Siri executive, the first being Dag Kittlaus, another co-founder who took leave after the iPhone 4S was announced in October 2011.
Cheyer worked on the voice-recognition software Siri leverages to give accurate results from normally-worded questions instead of forcing users to memorize keywords. The system is not perfect, however, with some users complaining it doesn't function as advertised by Apple.
Apple acquired Siri in 2010.