hi s.r I think that burials and headstones , which, for some reason we were never told where they were buried - is a problem - but there are people out there ( me included ) who are trying to help with sites and putting pictures on.
There are several things that have gone one in the past -and are still going on - some burial grounds have been 'reclaimed ' by the council and they have got rid of old gravestones and put a common 'memorial' somewhere else -
some old 'churches' the same thing and folks have been moved-
If he died in a workhouse he MAY have been buried in a common grave - but there will be a list of names so its not a lost cause - there are one or two websites free but its worth also asking your local council
(may be able to throw you in the right direction)althought i expect youve already done most of this already by what you have said.
Its worthwile to carry on your search as i have similar problems with one of mine (read post)
if hes not buried with them you will still probably be able to have his name inscripted on the stone with his parents as a memorial so that your future generations will be able to see it - but it cost a bit more to have that done than it did in the old days as they have to have a stone mason to do it and they are a specialisted trade these days -