I suppose it depends on the beardie. I wouldn't have thought they'd be inactive for more than a day (im sure someone will correct me if im wrong). For example, when thats happened with mine she'll just slob around until she goes to bed and then be fine the next day.
Just make sure after you feed them they go under the basking light for a few hours to digest
Most likely check and make sure your basking side is 100-110 and your cool side is 80-90 Needs to be a 20* difference they like it hot during the day I just had to replace my heat lamp with a spot light heat lamp 100 wat becuase my 50 watt wasnt giving out enough heat