I could be wrong but I believe that TDY orders are not considered permanent records in the service file. You may have to check with morning reports.
Dear Mr. Ellis,
Thank you for posting your request on History Hub!
A copy of these records should have been placed in your Official Military Personnel File (OMPF). OMPFs and individual medical reports for those who served in the U.S. Armed Forces during the Vietnam War are in the custody of NARA's National Personnel Records Center in St. Louis. In many cases where Army and Air Force personnel records were destroyed in the 1973 fire, proof of service can be provided from other records such as morning reports, payrolls, and military orders, and a certificate of military service will be issued. Navy and Marine Corps OMPFs were not affected by the fire. Please complete a GSA Standard Form 180 and mail it to NARA's National Personnel Records Center, (Military Personnel Records), 1 Archives Drive, St. Louis, MO 63138-1002. Veterans may use eVetRecs to request their own records. See eVetRecs Help for instructions. For more information see Request Military Service Records.
Also, we searched the National Archives Catalog and located Muster Rolls and Personnel Diaries of U.S. Navy Ships, Stations, and Other Naval Activities, 1/1/1949 - 12/31/1971 in the Records of the Bureau of Naval Personnel (Record Group 24) that may include muster rolls for the U.S. Naval Communication Station, Philippines (NAVCOMSTAPHIL). We also located Muster Rolls and Personnel Diaries, 1/1941 - 12/1980 that may include muster rolls for NAVCOMSTAPHIL's Marine Support Battalion. Muster rolls should include a record of you either leaving for TAD or being received for a TAD. For more information about these records, please contact the National Archives at College Park - Textual Reference (RDT2) at Archives2reference@nara.gov.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RDT2. Also, the NPRC is currently only servicing emergency requests associated with medical treatments, burials, homeless veterans, VA Home loan guarantees, and employment opportunities. If this is urgent, please see Emergency Requests and Deadlines. We apologize for any inconvenience.
We hope this is helpful. Best of luck with your research!