Yes, that's possible. It could be that what we're looking at on the planet surface is the output of a huge planet-sized radiator, with a civilization living in air-conditioned comfort underneath. But the problem with that theory is that you can't actually use the whole planet as a radiator. You can only use the space-facing side. You have to use the sun-facing side for energy harvesting. That temperature gradient would show up in the spectrum, and AFAIK it's not there.

[UPDATE] I don't actually know if current exoplanet observing technology is capable of detecting such a temperature gradient, but given what I know we can observe I'd be a little surprised if it couldn't. A planet-sized energy harvester would make a pretty big dent in the passive thermodynamics, and detecting that should not be too hard. And it would be Really Big News.