Interestingly, when I went to Security Preferences there was an icon to show that Apple Maps had used my location in the last 24 hours. This is in spite of almost never using Apple Maps on my MacBook, and certainly not in the last month. So this smells like some sort of background daemon or similar.
While some platforms go through the Maps app to get the location, under macOS/iOS there's the locationd daemon that provides the location independently of any app. There, Maps is just a locationd consumer just like any other app requesting a location so Maps shouldn't be invoked in the background by non-Maps stuff. But perhaps Maps has a timed trigger to background update your cached location (so it can open up to the correct startup location instead of locating you after startup) or something similar.
Did you hop into a vehicle you have paired with bluetooth? Apple Maps drops a "parked car" pin automatically when you do, I think regardless of whether it was in use at the time.
Maybe you used an app that uses an Apple Maps view?
Do you have any of the drive-time/traffic condition widgets active in the lefthand thingy, or homescreen?
