LOTS of info here if you are stuck in either the “debug plains” or the “debug forest”. I have been in both and it sucks. Follow the tips put together by kilcunda over on Reddit.com and you will be out of there in no time.
Remember: the clouds move from west to east! One way to get out is to run east till you hit Zelengorsk.
This is a very frustrating problem, it has happened to me a couple of times. If you are in the debug forest (has lots of pine trees around) and you know which way is east then just run that way. You will pop out on the southwest corner of the map.