it was fairly large and stationary, much larger than most spotlights. and, from my experience, with high-power lights like that you can usually see the, like, profile of the beam all the way light refracting off of small particles or the moisture in the air or whatever.

the only explanation I can come up with is that it was just garden variety suburban light pollution, just a strangely concentrated, very blue instance of it, caused by some group of nearby buildings. the biggest candidate is the medical centre which would make sense for the timing, since they'd obviously stay open past midnight.