Only when you work with "structured" code which you edit with the section editor then there is something like warm start files available in the temporary directory of the AppBuilder session.
On top of my head I don't remember how this files are named, but I do know that their name includes the name of the source code file you've edited. You could look for files in your session temporary directory which include familiar source code naming patterns in their name ...
AFAIK, when you've edited the code in the procedure editor there is no such thing available and you are hosed.
Heavy Regards, RealHeavyDude.