Short Final: Mirage Alert

I was inbound for landing at Reid‐Hillview airport and had a traffic alert off to my left, 300 feet higher and faster. About a minute after the traffic alert the tower told me I had traffic above and to the left of me. I replied that I did not have traffic in sight. Tower said, “It’s a Mirage.” I replied, “No wonder I can’t see them,” eliciting a chuckle out of the tower guy.