This is sourced to the DNB off a website:
"Lord Liverpool conferred on Napier the small non-resident and sinecure government of the Virgin Isles, in consideration of his wounds and services, and he held it for a year or two; but when pensions for wounds were granted he resigned it."
This is supposedly after he returned home in 1811 to recuperate and while he held the Lieutenant Colonelcy of the 102nd Foot [27 June 1811]. I do not have his bio handy.
As far as pensions go, there does seem to be many contradictions. Haythornthwaite states that the pension was granted for the rank held at the time, except when holding brevet rank and acting in a capacity in that rank at the time.
Dalton gives for Lieutenant James Crummer 28th Foot that he was wounded at Albuera and when he applied for a pension in 1832, for which he was entitled, as the wound was now causing him pain, was turned down "on the ground of the lapse of years since the said wound was received."
Definitely an area that needs work.