If he was born in 1831 then he was unlikely to be baptised at St Barnabas which wasnt built until 1832 (see http://www.ee.surrey.ac.uk/Contrib/manx/parishes/do/douglas.htm)
for which the first baptism is recorded in 1833 (see http://www.ee.surrey.ac.uk/Contrib/manx/famhist/genealgy/church.htm) - I have never heard anyone else say the the records are missing (the church maybe, being demolished some 40 years ago and now forming an unattractive carpark/walled bare patch in front of the only slightly more appealing bus station (this bus station site occupies much of the heart of old Douglas! though I suspect its days are numbered and yet another office block will take its place)
He was most likely baptised at St Matthews (the old one that is - again demolished but this time buried under the British Legion club adjacent to the Bus Station)