It looked like a window and door less propane tank in the sky

We were on our way home when it looked like a bright star in the sky facing south but when it changed we relized it was a reflection on a solid white surface of somthing moving very fast in the sky we recorded and followed it until it became much faster and vanished a few days later we had seem the same thing on the exact same path as the one before unfortunately we did not have a camera at the time.