Japanese seemed to move aircraft carriers and cruisers to the east or back to Japan according to the U.S. Joint Intelligence Committee Daily summary dated 15 May 1942

An item reported that aircraft flying over the New Britain-Solomon Islands sighted on 13 May a large number of merchant ships at Rabaul and several small naval units and transports near New Ireland, Buka and Bougainville. A large ships which could be an aircraft carrier with air protected overhead was seen near Tabar Island east of New Ireland eastward bound. Since several days were no large numbers of carriers or cruisers sighted, probably indicating that those went to the east or back to Japan.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 156 dated 15 May 1942