Am I screwing things up by leaving the 'place' mat out and then my dog going to her place and not getting rewards? Or does she know that rewards only come with the command?

I purchased your dog obedience video.

Question (re: Place) -- I leave her "place" mat out all the time for her to lay on (even when we are not working). On occasion, I've turned around (while not working the 'place' command) and see her down sniffing between her paws. She's a 7.5 month old Doberman and when she realizes I'm looking she gives me that tilted head Dobie velociraptor look ('hit me up bossman'). Ordinarily, I would view this as good (if we were working) and mark/reward her. But in this scenario (timing), I do not even know (1.5 seconds) how long she's been in that position.

Am I screwing things up by leaving the mat out and then her going to her place and not getting rewards? Or does she know that rewards only come with the command? I'm confused because Ed said that the rug should be given value.

Help.