I worked for a year in Manhattan and stayed at a hotel with those *%$#@ thermostats.

I discovered (after a bit of experimentation) that I could disable the IR sensor by shorting two of the 3 pins that connected it to the main circuitboard. Had to remove the cover, and in the case of this particular model of thermostat, the 3 pins projected from the bottom of the sensor and took a 90 degree turn into the circuitboard. Short the center pin to the right pin and the sensor was bypassed.

A set of RadioShack Mini Clip Jumper Wires did the trick nicely (they come in sets of 2, but you only need one).

I was careful to remove it before leaving the room for the day; it was pretty obvious dangling from the thermostat.

PS. The thermostat cover was usually held on with two hex screws, but a bit of patient wiggling would work the cover loose. Easy to replace, too, with no one the wiser . . .