Database level health check did not trigger failover on losing a disk
On the primary node, I took a drive offline that contained one of the data files of the DB that is in the AG. I ran a select * from a table which read from the missing disk [...]


Since you're on 2016, the database level health checks are checking that the database is online (which taking secondary file offline won't change) and that we can write to the transaction log. Since both of these are true, your test passes. That's how it works in 2016.


  Any idea where else I should be looking for why this did not fail over?


Yes, see above. This was changed to encompass more in 2017.