The evening-shift work on the airplane was documented on the shift inspector's written turnover sheet. However, the incoming midnight shift inspector reviewed the sheet before the entries were made. The midnight shift maintenance supervisor and mechanics were not verbally informed of the removal of the upper screws on the left side leading edge. The midnight shift continued with the right side assembly. The supervisor's attention was diverted to an urgent task on a different aircraft; he prudently instructed the mechanics to finish work on the right side only, and to delay starting on the left until the following day. The aircraft was released with a total of 47 screws missing from the left leading edge.