We had a commercial water loss that had a mysterious odor. A very sour odor like a sour dish rag or the smell similar to laundry left in the washer overnight. Everything was dry as we Thermal scanned the room. We had cleaned the carpet and thought possibly they had closed the room up. After checking the carpet, it wasn't the source of the odor. After closer inspection we discovered the culprit. A single ceiling tile had a water stain on it. In the darkened area the odor was just awful. The one tile mad the whole room smell horrendous once closed up. Have a phantom odor? Look for a water stained ceiling tile.