I would call 911 and report it stolen if it truely has been stolen and contact the Merecedes or alarm company to let them know it needs to tracked down. I would do it now if you have not so already otherwise your car could already be getting stripped or shipped.
Good luck i hope you get your car back.
Looking for a Used E-Class in your area?
CarGurus has 19,715 nationwide E-Class listings starting at $1,200.
Search Mercedes-Benz E-Class Questions
Mercedes-Benz E-Class Experts