Chances are it's bubbling because the air in the headspace of the carboy is expanding as it warms up!
Chances are, it is/was fermenting. The krausen was starting to form and everything. I know it's a rookie mistake, but it's not my first batch.
That being said, be careful what you wish for! I woke up this morning at 6:00 to check on it and make sure everything was ok. I got into the kitchen and heard a hissing noise. WTF is that? Turn the corner, and I was lucky enough to catch it right as the krausen worked its way into the airlock. Ok, I'll just take some tubing and make a blow off real quick, simple, right? I don't know if I mentioned that I sold all of my brewing equipment and decided to get back into it pretty low key. The ONLY tubing I had was the piece for the auto-siphon. I cut it off quickly and tried to jam it on my airlock. They are the exact same diameter, ****! What do I do? What do I do? I tried heating the tubing up to get it to stretch a little bit - no bueno. My LHBS is closed, Lowes and Home Depot are closed, its 6:15am and I don't want A) to lose this batch and B) to have it explode all over my kitchen...
Solution - Not the best one, and probably going to be an addition to Revvy's thread of mistakes, BUT, I did it. I'm not proud of it, but it'll work until the LHBS opens and I can get some more tubing. I took a standard Bic clicking pen, pulled the guts out of it, took the clicker off and the pointed end. I was left with about a 5" long straw that had an OD about 1/32" smaller than the ID of my tubing. I washed it really well, hit it with some star san, and then I used it as a coupler between the stem in the airlock and the tubing, taped the hell out of it, and the batch is successfully blowing off into a jug of water. I had to cut off the outer shield on the airlock so I could put tape around the stem on the inside, as well. I'll be in the parking lot when my LHBS opens to get some more tubing and a handful of air locks!
I'm thinking - Boomer's Black Botch is going to be an appropriate name for this one when all is said and done. At least I didn't burn myself while boiling, that's ONE good thing so far!