I suddenly changed my mind about capital punishment. There's no note left by the offender.
Luckily there's no other damage than the mirror, and due to the plentifulness of Peugeot parts I doubt this will cost me more then €15. It still sucks though.
The Peugeot was parked very closely to the curb and since it's narrower than your average other car I find it surprising this happened.
Here it is, parked in a similar spot before being molested.