Post-WW1 Philippine Postal History Markings

This rather unfortunately beat up undivided back RPPC was sent from Manilla in the Philippines to Fort McDowell, Angel Island, California in 1919 with some markings completely new to me: 'No record at HQ Phil Dept' which is somewhat self-explanatory, and 'Philippine Replacement Troops, Manilla, P.I.' which is a complete mystery to me.
Can anyone expound upon these military markings, especially the latter?

I believe the original point of mailing is from some "M" town in the continental US. There are several "Fox River" possibilities.
Sent to California, then forwarded to the Philipines, where they had no record.