So, I have 2 corny kegs going. One had about 3 gallons of hefe in it fully carbonated and sitting at 10 lbs. The other was a stout that I force carbonated for 18 hrs at 35lb. Today, I woke up feeling tired and knew I had to stop force carbonating the stout. I came out to the fridge and hooked the co2 line back onto the hefe keg without turning down the pressure! I heard a hell of a noise and in an "oh SH#T!" moment I turned down the pressure to 10lbs. Now, my hefe has some stout in it! I thought the corny kegs had a check valve to stop beer from going up the co2 line. ??? Any insight or advice would be appreciated. Thanks.