You didn't mention having checked local church burial registers; considering the early year there are not many churches to chose from. The burial register records the event of the burial - and is not the same as a cemetery record (which should be an inventory and location of a plot). The detail included with those registers varies as with any record.
I have evidence of this from my own family research in Milwaukee. I have constructed some of my earliest finds through parish burial records: most, but not all finds were previously unrecorded children. (In fact, in two cases, I've been able to confirm the number of children living/deceased referenced in later census records by using early church records - baptism or burial records.)
For a German Catholic family located in Milwaukee in 1849, the likeliest place to look would be "Old" St. Mary Catholic Church (filmed by the LDS). Their early records include German immigrants from a wide area. Someone else may have advice on the early local Protestant churches.