I have found that the four lifeguard submarines for the May 25/26th B-29 night mission (positioned from north to south) were:
USS Razorback:
https://www.fold3.com/image/300721210
http://aimmuseum.org/wp-content/uplo...r_Patrol_4.pdf
USS Pipefish:
https://www.fold3.com/image/296541981
USS Dragonet:
https://www.fold3.com/image/296106717
USS Tigrone:
https://www.fold3.com/image/296528894
Each submarine would generally have one or two air rescue Dumbos (B-17s with droppable lifeboats) or SuperDumbos (B-29s with lifeboats) assigned to “ cover” them. The Dumbos (call signs BoxKite-1, BoxKite-2, etc) would serve as eyes and ears in the sky for the submarine. Reading though the War Diaries for the four submarines, we learn that the submarines often had radio communication difficulties and radio/radar/sonar failures while trying to perform their lifeguard duties.
Lifeguard duties were not only for the night B-29 raids, since during the day long-range fighter strikes were flown to Japan by fighters based on Iwo Jima. The fighters would have a B-29 with them (call sign Dreamboat) which would lead them to and from Japan. The day time and night time lifeguard stations for a submarine were typically either the same locations or close to each other.
Robert Mann’s book, “The B-29 Superfortress Chronology, 1934-1960” can be viewed or downloaded from here:
https://epdf.tips/the-b-29-superfort...1934-1960.html
Starting on pdf page 183, (book page 172) there is a list of all the planes lost on this mission and their fates. It turns out that the fates of all but two of the losses are known, those two are:
42-63521, 58BW/462BG/769BS, Possibly named (Li’l Eight Ball) . Tail code Triangle U #32, Missing from Tokyo. MACR is here:
https://www.fold3.com/image/46753149
(The MACR is interesting because the family of the pilot, Major Ellerbe wanted some answers.) Call sign would have been “Wicked-32”.
42-65273, 58BW/444BG/677BS, “Big! Aint It?” . Tail code Triangle N #62. Missing from Tokyo. MACR is here:
https://catalog.archives.gov/search?...estorNaIds=421
Call sign would have been MASHNOTE-62.
From the War Diary for the USS Tigrone we read that they were on their lifeguard station, (30 00N, 140 00 E) when at about 0300 on the 26th, they track many B-29s headed south. Some 15 of the planes have their emergency IFFs turned on. This will make their blip on the sub's radar screen appear different than a normal "friendly" blip with normal IFF on or even a non-IFF blip. One plane’s emergency IFF suddenly goes off the air about 40 miles “to the south”. This “vanishing” IFF is confirmed by Bird Dog 1, a rescue surface ship located further south. (What they are seeing is not a plane turning off an IFF, i.e. the then plane's blip remains on the radar screen, they are saying the plane with the IFF signal vanishes.) Tigrone’s VHF radio “had given up the ghost and (they) could not find the problem”, so they cannot contact any of the returning B-29s. The air rescue circuits were working, however. Tigrone’s war diary notes: “It was heartbreaking to know someone so close was in trouble and nothing could be accomplished because of poor communications.” At noon on the 26th the Tigrone is on station for the daytime fighter strikes. By 1400 the strikes are over. USS Tigorne requests and receives permission to head south and search the area where the IFF vanished at 0300 that morning. At 1910 on the 26th the submarine reaches the search area and commences a search running parallel legs 2 miles apart. At 2335 they get a radar contact which turns out be a Japanese patrol boat. They fight a long running gun battle with the patrol boat which is described in some detail in the diary. There is no more mention of the vanishing IFF and the war goes on.
On the 27th the Tigrone is back on lifeguard duties and on the 28th is involved in a series of rescues.
So, it is possible that one of the two missing B-29s went down some 40 miles “south” of the Tigrone’s lifeguard position on the 26th.