I received an e-mail from Ray about my 1645 kHz log on the Twente receiver. Yup, it was not Misti Radio, but rather someone playing a song for Misti. Here's the e-mail:
Your station on 1645 kHz logged at 1650 utc on Jan 30th is not Misti Radio, but Zender Concorde, playing hard rock, including German rock.
You can hear it again through the site of achimbrueckner, with a recording beginning at 1641 utc (after two shorter ones of the same station). That is a very good recording, just a bit of noise. At about 11min42sec, the DJ says "OK Misti..." and more in Dutch, agreeing about a request for a record from Rainbow. Then playing that record, I think (I don't know really that rock group).
I did not hear an ID of the station, but I'm pretty sure that Achim could not be wrong on such a good reception.
Many thanks to Ray for the clarification and research!