Unfortunately it seems we killed most of our stats. 
We had m4a and mp3 downloads for a while. Then we wanted to go mp3 only. My colleague deactivated the assets first and after a while he deleted the old m4a … suddenly our stats are half gone (which makes sense, I guess).
Is there any chance to get that back?
Not sure. Do you have backup of the former state?
I fear no (also checked the provider). Putting back the m4a also didn’t help.
The stats are probably still there, just disconnected from the assets. What you can try is recreate all assets as they were before, then change their IDs in the database back to what they were before.
You can probably guess the old ID by looking at the data. If you only ever created two assets, and mp3 is id 1, then m4a should be 2, and vice versa.
I can’t believe it! @ericteubert’s tip did the trick! After some investigation and trial and error we could get the downloads back! Big 
️!