Its creator noticed it was gone from the top of Waterin' Stane cairn on Christmas day and has issued a plea to get it back.
The Cornet leads riders to the boundary stone, which had previously stood for over 10 years, before stone mason Andrew Hume created the new tower in July 2019.
Now he just wants it returned in one piece. He said: "Someone could have rolled it down the other side of the hill or smashed it to pieces or it could be in the boot of someone’s car and they’ve completely forgotten how it’s ended up there.
"I was quite shocked really it seemed like a petty thing to do to take something someone has created from the side of the road. It was a bit of bafflement really, especially for Christmas day, for me to come and find that it was quite annoying."
Every year the monument is used in the Lauder's Common Riding events.
It's one of the original Border Common Ridings. Many believe the festival dates back to the 1600s, now it takes pride of place in the Lauderdale calendar.
Andrew said: "It’s something I’ve created. I’d like to say the town is quite proud of it and I’d like to see it standing here, or my children to see it standing here, for one hundred years’ time. I’d like it to be brought back and returned."
A group dedicated to Lauder Common Riding broke the news on their Twitter feed, they said: "The top stone from our cairn at the Waterin' Stane has gone missing. Andrew Hume did a great job for us and it's a real shame to see that hard work go to waste. We'd love to see it returned."