The question is about the photons that were left bouncing around the room just before the light was turned off.
Those do have to go somewhere. In a perfectly mirrored room, they would continue to bounce around until you yourself absorbed them all.
It's kind of like a little problem I used to wonder about... If you take a box outside and close the lid, at least some of the photons should be trapped inside (reflected off the closing lid back into the box). And yet, inside the box, once you close the lid, it's dark.
Actually, that was the subject of a Chelm story, where the villagers try to capture light in barrels to store for the winter.
Of course that doesn't work, but I always wondered what would happen if you tried that with a mirrored box.
But then, even if it did work, all the light would escape (at the speed of light) as soon as you opened the lid, so that wouldn't really do too much for you anyway.
All of which goes to show you that the best way to store light is in a solar-powered flashlight. (Which, joking aside, actually does exist... You charge it with a solar cell during daylight so that you can run it off of battery power at night.)
