OK. The old display was picked up last Thursday (September 8, 2016). Now I have a FP2 without display. No reaction from Fairphone after pick-up yet.
I looked now into the package tracking:
The package arrived already Friday afternoon at Fairphone.
Edit (2016-09-13 10:52): I do not see my return request in the return portal anymore.
Edit (2016-09-16 10:00): Still no reaction from Fairphone yet.