Rather strange coincidence, but I am pretty sure that there was a Thomas Lanphier (1779 - 1823) who served as Lieut Colonel in the 86th Regiment of Foot or Royal County Down, whose headquarter was probably stationed at Dublin. He died on 20 May 1823 and buried in Ballymurren graveyard, shortly after he retied by sale of his commission on 23 January 1823. He was largely responsible for the coat of arms of lanphier from Betham, Uslter, for his greatfather,who is, as I identified from some other source, Joseph Lanphier (1702 - 1772) & Anne Foulks.
I got the information from Richard Cannon's Historic Record of the Eighty Six or The Royal County Down at the National Army Museum in Chelsea, London.
Perhaps, you could get some good information from this museum on your great great grandfather, Lt. Col Joseph Lanphier (1782 - 1838)