I went through a 8 hour power outage and had no ill effects. I would stir the water when I was near the tank to help with oxygenating but other than that all I could do is wait. I would test your water several times over the next few days and do water changes if necessary.
hmm.... i never even thought about that.... our power was off for a week this winter with the ice storms, I had to pull everyone out and shove them into my inlaws 29 gal tank.... that was fun!.... but when the electricity came back on and the temp got back up to normal from 35 deg., I just did a water change and put them all back in. I only lost 3 fish and that was it just got too cold for them before I could get them out.
As long as your wheel was still damp, you should be fine. Biowheels are great becuase in the rare occurance of a longer outage, you can just toss the biowheel itself into the tank water to make sure it doesn't dry out.
My power went out for a whole day a couple of weeks ago. I went to the LFS to buy a battery powered air pump with airstone. When I got home, lo and behold, the power was back on. At least I'm prepared for the next outage with the battery powered pump to oxygenate the water. I guess it wouldn't do anything for the bacteria colony though.