Recently, I asked for credit for a flight that did not show up in my "activity since the last statement" and was told I had received credit already. Here is my further exchange with CO:

ME: "[Referenced flight] does not
show up on my online "activity since the last
statement." Is it possible that it is in the system
so that it will be on my printed statement, but is not
in the online system?"

CO: "Yes, that is correct. I double checked your account and it is in the
"master system" but still may not show up yet online. The online
version is almost like a photo of a future statement and flights are slower to
show up there. Also, I don't think it is yet perfected as I have seen a stray
flight missing online yet it will be on the next statement and also
appear in my corporate system."