With 70+ minutes of flight time, maybe it wasn't battery powered but rather powered with liquid fuel.
We should be long past the point of uncritically believing everything police claim.
They also made visual contact with the light on the underside of the drone: "From what I can tell just from its position light, you know, I would have to imagine it was larger than a quadcopter"
Military primary radar, like the one that picked up MH370, obviously can.
But I don't think any of those are designed for really accurate altitude measurements. That job is usually done with targeting radar which (at the expense of not being able to see multiple targets) can lock a single target and get it's exact position.
night vision systems are , most typically, very low-light sensitive cameras that occasionally have specific-wavelength illuminators -- they aren't generally thermal cameras.
I tend to think something with a run-time like that is liquid fuel based, too.
It's likely they had thermal cameras available. There is a lot of video of police helicopters using thermal imaging to track people they are chasing.
The audio I linked to makes me think they tried to use it but couldn't see the object.
It's more likely there were multiple drones swapping in and out.
In the report[1] they explicitly list it has as a rotocraft with an unknown (-1) number of rotors. They also list the UAS type as "quadcopter". At one point in the article they describe it as "hovering"
[1] https://s3-us-west-2.amazonaws.com/the-drive-cms-content-sta...