Lost Pet: Dexter

Circumstances

Dexter is an indoor/outdoor cat.  He comes in at night and goes out during the day and usually stays very close to home as we live on 7 acres but in a neighborhood.  He was last seen at about 7pm in the evening on Monday April 28th near our house.  When we called him in for the night about two hours later, he didn't come.  He usually responds to my voice immediately but no amount of calling for him worked.  We've scoured the neighborhoods and all the land around our house with no signs of a struggle or anything.  He did not have a collar on so maybe someone thought he was a stray and picked him up?  He is microchipped.