Sorry to get on that tangent Johnny.
Easiest to shut it down is to flip the switch.
If you really want to turn off via the thermostat, you can set the IGN setting in SETUP to M, and then use the BRNOUT operation in the extended operations menu. To get to BRNOUT, make sure IGN is set to M, then press and hold the menu button for 5 seconds, until the "FEED" screen shows up. Then click the menu button two times (FEED -> IGNITE -> BRNOUT) then press the up or down button to activate the burnout operation. It will say "BO# ##", where the first # is the phase number and the second is the total number of minutes left in the operation. When it is done the motors will be stopped and the fire should be mostly out (still warm or even hot, but out). To reignite go into the SETUP menu and set IGN back to N. The motors will start up like normal and you can use your normal fire starting method. This is a complicated way of doing it, using stuff intended for use with the optional Igniter Kit, but it will get the job done.