Some bakers miss blocks. How can bakers retroactively check whether their misses were steals? Tzscan does not seem to differentiate between misses of Prio 0 (proper misses) and misses of Prio>0. Is there a way to retroactively check a bakers assigned ops priorities - including the missed ones?
It is not possible to directly retrieve from the RPCs the information you are requesting. Some public services index chain metadata in order to be able to provide extra historical details.
For example, in the current cycle 153 you can see that bakendorse displays the priority level of the missed bake. But they choosing to only display this information for the current cycle.
Here is a baker with a priority 0 miss, if you know a baker with higher prioriy miss you can search for them on bakendorse https://bakendorse.com/#/bakers/tz1dFdxNnfr2HpQkpfEAcSCEVGXEhtbxaHxM/dashboard