Thanks for all the info so far.
OY-1 with lost pilot on 19 Jun 1944 must have been BuNo 75159 according the AAIR database.
US Army 27th Infantry Division fought alongside the USMC 2nd and 4th Marine Division.
DIVARTY has a detailed report of its Saipan actions on
https://museum.dmna.ny.gov/applicati....2019.0003.pdf
Looking for any pilot or observer losses, there's one observer missing in a TBF in the 291600-301600 June timeframe (294th FA Bn = Lt James W. O'Neil) and a liaison pilot between 011600-021600 July 1944 shot down in a Navy plane (TBF?) (106th FA Bn = Lt George Sandburg).
Annex D provides more details about the L-4 operations. It transpires that up till end of month the pilots/observers used Navy planes and that two DIVARTY pilots were lost. See 4. Summary of Annex as well that no L-4's were lost on Saipan.
Will look for B-25/PBJ on Saipan.
Regards,
Leendert