It is Findmypast rather than Ancestry that have the majority of records from this period. If there is nothing on FindMyPast it is likely that he was not awarded a pension.
The muster books are what you need, but they are not on line. If you can not visit the National Archives you will have to employ a researcher.
Starting with the muster for the 1st Battalion in 1834 you can work forward until he leaves or dies. He should have a number by this time. Which will make it easier to get something from their archives.
Ken