She was not heard from after 19 August 1943, and on 30 September 1943, GRAYLING was reported as presumed lost.
Following the war's end, the Japanese have submitted the following reports which bear on GRAYLING. On 27 August 1943 a torpedo attack was seen by the enemy at 12! -36'N, 121! -33'E, and the next day a surfaced submarine was seen at 12! -50'N, 121! -42'E. Both of these positions are in the Tablas Strait area. On 9 September a surfaced U.S.Submarine was seen inside Lingayen Gulf; this ties with GRAYLING's ordres to patrol the approaches to Manila. It is said that the freighter-transport Hokuan Maru was engaged in a submarine action on the 9th in the Philippine area, but no additional data were available, and no known enemy attacks could have sunk GRAYLING. Her loss may have been operational or by an unrecorded enemy attack. At any rate, it is certain that GRAYLING was lost between 9 and 12 September 1943 either in Lingayen Gulf or along the approaches to Manila. ComTaskFor71 requested a transmission from GRAYLING on the latter date, but did not receive one.
GRAYLING's first war patrol, made in January and February
1942, was a reconnaissance of the northern Gilbert Islands. She went to
the Japanese homeland for her second patrol, and sank a freigher and damaged
a sampan. Truk was the scene of GRAYLING's third patrol; she sank
a large freighter. On her fourth patrol, this boat again went to Truk,
and sank a medium tanker, while she damaged an aircraft transport. In January
and February 1943, she patrolled the approaches to Manila on her fifth
patrol. Here she sank two freighters and a medium freighter-transport.
GRAYLING patrolled the lesser islands south of the Philippines on
her sixth patrol, and sank two freighters, a small freigher-transport and
two schooners. She went to the area west of Borneo for her seventh patrol,
and sank a medium freighter and two sampans. Damage was done to a large
tanker. Thus GRAYLING's total record is 16 ships sunk, totalling
61,400 tons, and six ships damaged, for a total of 36,600 tons.