I too would suggest getting Kathy Love's book and some NutriBac for you little one. You can order both fro her website for a very reasonable price her is the link...
http://www.corn-utopia.com/Corn%20Ut...cornsnakes.htm
As well, it has already been noted that the regurge may have been caused by handleing before the meal was fully digested, generally a very good way to tell is wait a min of 2-3 days from when you fed or until the snake has pooped once for you. With small hatchlings the poop is often so small you can not find it in the substrate, so 3 days is a good rule to go by.
Better yet though, esp. now that it has had a regurge, is to clean out the viv and use paper towel for bedding. This way you will easily and quickly be able to spot another regurge if it happens again and you will also know for sure when the snake poops thus making sure you do not handle to early. I would do this until you are done the regurge protocol and have learned your snakes general digestive timing.
I would also like to point out that you mentioned your warm side is at 80, this may also have caused the regurge. The general optimum temp for the warm side 83-85 and if it was at 80 you corn may not have had enough belly heat to fully digest the mouse before it rotted in the belly. Therefor I would suggest raising your warm side temp and keeping it between 83-85, make sure you are checking it with either an infrared temp gun or a digital thermometer as the stick on strips or dial ones are notorious for being inaccurate by as much as 10-20 degrees either way (which both to cold or tow hot can cause a regurge).
Once you order the NutriBac, which is a reptile probiotic, mix some into the drinking water and then change the water daily. Then on feeding day do tow things different, get a sharp paring knife or some cuticle scissors and cut through the skin on the back of the mouse, this allows the stomach acid quick access into the mouse to aid in digestion, helping to prevent it from rotting in the stomach. The other thing you should do is place some of the NutriBac powder just under the skin of the mouse and then give the mouse to your snake, this ensures that your snakes stomach bacteria is aided in getting back to healthy balance, use the NutriBac with either every or every second feeding during the regurge protocol. The reason I am suggesting this is because every time a snake regurges, it vomits out most of the stomach bacteria, good and bad and then the gut flora become out of balance and the bad bacteria can flourish and take over making the snake ill.
I have used the NutirBac with 2 snakes who had digestive problems and I believe that for the one it was the cause of the balance and for the other I KNOW that it saved the hatchlings life. That hatchling I fostered for a pet store in the next city, the hatchling had regurged twice already, its spine was sticking out, it was lethargic and not eating for them. I brought it home started NutriBac therapy and then Reguge therapy and sent it back to them exactly 3 mths later a very strong, healthy, muscular, aggressive feeder who had gained 15 gms and not had a single regurge while here.
Hope all of this helps you and your new baby out. Sorry if it was long winded.