Corporal Corriveau had served in Viet Nam, where he was wounded in 3 separate battles. On the third occasion, he was medevaced out of Vietnam for treatment of his wounds at Naval hospitals.
After a time, he was sent home to his parents' house in Massachusetts on convalescent leave. He was offered an early honorable discharge from the Marine Corps, since he only had a short time left on his enlistment. Robert, however wanted to stay in the Corps, and maybe reenlist.
Unfortunately, Robert was suffering from what we now know is PTSD, and was readmitted to the Naval Hospital for treatment - this time in Philadelphia. He arrived there on 17 October 1968.
It seems that he might have left his ID and dog tags at home. If that was the case, he was probably issued new ones in Philadelphia. He certainly would have needed an ID card to check in
Every military ID card has a date of issue on it, as well as a "valid until" date. If The ID card in his mother's possession was issued before 17 October 1968 (as I suspect it was) then it was left at his home when he was taken to the Philadelphia Naval Hospital - where a new ID card would have been issued.
If he had left an ID card at the hospital, it likely would have been placed in his Service Record and transferred with it on or about 18 December 1968 when he was declared a Deserter. It definitely would not have been sent to his family.
I think that whoever murdered Robert kept or disposed of the ID card. he was carrying at the time of his death.
and out