I'm so, so sorry! It's a horrible feeling when pup goes missing.
When Bacca took off in the summer for his island adventure, I was so sick at heart, I thought I was going to be physically sick. We searched for hours, and just when despair hit, he came bumbling out of the woods like nothing ever happened!
Good karma going out to you that you find Oliver soon! The boys and I are sending you huge Sheltie hugs.
Do you know what sent him off? It might give a clue as to how to get him back.