Lost Pet: Cooper

Circumstances

Cooper was outside overnight with an electric collar. We live on a 50 acre farm and this is used to keep him around the house - even without the collar he never goes beyond fields/trees near the house. I came home around 2pm today and he is missing - I have found no sign of the collar. I have two older female dogs in the yard who are still here - even if the collar stopped working, he would not have left them. I have driven the roads near the farm and I have not found any sign of him. I am worried he has been taken by someone - possibly a person named Michael Grooms as we were in a relationship several years ago and he had asked to see Cooper on a few occasions, which was declined. He is wearing a collar with his name and a phone number as well. All information on this account is up to date. Please help me find him.