Thank you, Rolland!
Outstanding research as usual by you hunting the details of these lifeguard subs. These USN War Diaries certainly make for interesting reading. (still reading those identified by you).
The loss of B-29, 42-65273 “Big! Aint It?” may remain a mystery but it is certainly not from the lack of your trying to find the facts.
For what little visual aid it is worth attached is the lifeguard chart for 23-26 May 1945 with lifeguard submarine locations by name added by me, identified by you.
Edit:
Interestingly the USS Haddock (SS-231) appears to have also been on lifeguard duty 25 May but is operating out of line with the other boats at 32 21 N, 145 55 E which plots about 390 mile east/northeast of the USS Tigrone at 30° 0'0.00"N 140° 0'0.00"E
It seems USS Haddock was also experiencing radio difficulties.
USS Haddock War Diary
https://www.fold3.com/image/296141440