If you want it back on the car, simply bring this to the attention of the dealer. They should give you a major apology and free oil change in addition to replacing the emblem.
Don't wait too long, though, or they may say it was not their fault it is missing. It is best to bring these things to the attention of the repair shop within 24 hours, for the best response.
PS. I prefer the 'original' look with all badges and chrome intact
76 240D (W115) - 550K miles
78 300D (W123) - 200K+ miles