The left main entry door departed the airplane after the pilot opened the door during flight to retrieve a carpet strap flapping against the airplane. The pilot was unable to hang on to the door and it departed the airplane. The airplane landed without further incident. Examination revealed the door contacted and punctured the right wing. It then contacted and punctured the right horizontal stabilizer. The emergency procedures section in the pilot operating handbook (POH) contains a warning which states, “Do not open the cabin doors in flight.”
