Richard Simmons' 'Slimmons' Closes ... No Sign Of Richard

Richard Simmons' Slimmons Studio held it's last class Saturday ... and the health guru was noticeably MIA.

Gym goers piled into the space for one last hoorah -- there was plenty of sweat and tears -- but Simmons, who's been out of the public eye for 2 1/2 years never showed.

We're told gym staffers shared a letter from Richard thanking everyone for their loyalty, and encouraging them to continue a healthy lifestyle without him.

Simmons' Facebook page has been very active recently, with posts from his time at the gym over the years.

At this time, it's unclear what the space will be used for in the future.