It has been removed because it got reset in a fight.
I'm not sure if it'll help, but there seems to be more than one representation for both Max HP and MP, and the ones that do matter are strangely not close together (I used Apples and Soma Drops, and went into a battle or two to check if the values revert or not).
Anyway, below are the addresses for the attributes I've discovered in CoSMOS, sampled from Dark Knight Cecil. The address structure should be the same for any character, as confirmed by the trainer (and by myself with another character, like Rydia).
Cecil (Dark Knight):
FF4.exe+2311C0 - EXP (4 bytes)
FF4.exe+2311C6 - Max HP (2 bytes)
FF4.exe+2311C8 - Current HP (2 bytes)
FF4.exe+2311D0 - Current MP (2 bytes)
FF4.exe+231386 - Strength (1 byte)
FF4.exe+231387 - Stamina (1 byte)
FF4.exe+231388 - Speed (1 byte)
FF4.exe+231389 - Intellect (1 byte)
FF4.exe+23138A - Spirit (1 byte)
FF4.exe+23138C - Max MP (2 bytes)
[Edited by FFFanatic, 9/24/2014 10:35:44 AM]