Ron,
Thanks for the links to the 1815 Royal Military Calendar. I had planned to download them anyway, so you have saved me searching for the links.
Any missing officers might not just have died, but also could have left the Army. A massive reduction started in 1814 (after the Peninsula War) when twenty-two 2nd battalions were disbanded and continued in 1815-16 after Waterloo with many more such reductions.
Rod