Mate that feeling of not being able to stop thinking about it is exactly how you know it was something worth paying attention to. The brain keeps returning to things it cant categorise.
What colour was the light, and was it making any sound at all? Those two details usually help narrow things down a bit. Plenty of conventional explanations for hovering lights but there are a few cases where nothing fits no matter how hard you try to explain it away.
I had something similar over Arthur's Seat here in Edinburgh a few years back, just a silent object holding position for maybe 4 minutes then gone. Still no idea what it was. Would love to hear more detail from you if you're up for sharing.