Why does AY912 not appear between 06.10.2017 and 22.10.2017

On the 18th of October 2017 I flew with AY912 from Berlin to Helsinki with a delay of, according to Finnair, 1 hour and 29 minutes due to apparent Berlin air traffic control regulation (fog) plus 1 hour and 58 minutes due to technical problems. Makes it in total, 3 and 27 minutes. I am trying to find out if the plane would have had delay even without the Berlin air traffic control regulation.

Unfortunately, I do not get any search results on AY912 and 18th of October 2017. Can someone explain why this is?

I have no idea, but I found the plane reg and with it I found the flight itself.
Have a look:
https://flightaware.com/live/flight/OHLZB/history/20171018/1501Z