That description of it just sitting there without moving is the part that gets me. You mentioned it was hovering - did it seem completely stationary or was there any kind of drift to it, like it was making tiny corrections to hold position? Because I've been looking into a case from this area about 15 years back where a bloke reported almost exactly the same thing, and the detail that kept coming up was this very slight wobble, almost like it was fighting a breeze but not quite managing it.
Also worth asking - what was the weather like? Clear sky, overcast? And roughly what time did you first notice it? The treeline detail is interesting because a lot of these sightings seem to happen at that kind of boundary, edge of woodland, edge of fields, that sort of transitional space.
Don't want to jump to conclusions either way but I don't think you should just let this one go without documenting what you remember now while its fresh. Write it all down even the stuff that seems insignificant.