After an uneventful local instructional flight, the student pilot and instructor pilot were practicing emergency landing procedures. After a missed approach to the private ranch airport, the student attempted a go-around. During the go-around, there was a loss of engine power during the climb and the student pilot tried to set up for an actual emergency landing. While maneuvering the airplane to land, both the instructor pilot and student attempted to trouble shoot and regain engine power by switching fuel tanks attempting a restart. About 20 feet above the runway, the airplane stalled, impacted the runway, and came to a stop in a grassy area to the left of the runway. Both wings sustained substantial damage. After the accident, the student pilot, who owned the airplane, stated that he may have moved the fuel selector lever to the left tank position while he and the instructor were trying to trouble shoot the loss of engine power. The instructor pilot occupied the right seat and would not have been able to see the fuel selector lever position. Postaccident examination of the airplane and engine revealed that both the right main fuel tank and auxiliary fuel tank had usable fuel. The left main fuel tank was empty and was not compromised. The fuel selector lever was found in the left tank position. No evidence of mechanical malfunction or any other preimpact abnormalities were found. Although the loss of engine power could be linked to possible fuel starvation, the cause for the loss of engine power could not be substantiated.