The plaque was historic to the island in the Hebrides the plague was given to the island in the 1936 and was listed as national monument on the 136 meter high summit.
It was only reported when a groups of children when to the area for their school trip. They went there to take a brass rubbing and found out that it wasn’t there. 30-inch plaque was vital in its own right but also had historical significance.
Mr Byrne said: “It’s a big loss to Colonsay and it’s pointless to anybody else. The plate is irreplaceable, but in view of its distinguished provenance its intrinsic value is considerably in excess of eight thousand pounds.”
A Strathclyde Police spokesman said: “Enquiries are continuing, we will be liaising with the community.”