Ah, that IS weird. :) Glad, you found the hickup, though. Good look getting the steam key!
EDIT: Woah. Our exchange goes into the Galaxy Champions Thread. I'll call the adminbulance!
thanks for your interest! There is no Steam-Version available, and there are no plans to publish 2nd Monster on steam at this time. So, no. No steam key included.
If you have other questions or feedback, let me know!
Have a nice day!