Not everything is online as yet and "experts" would travel to a place themselves to have a look for themselves. MO is one of the best states of putting state records online so if those sources are not locating them then there is something wrong with a name as written or transcribed or it would not scan properly and must wait for future technology. The best you can do is go yourself to search the county records or pay someone to do it. I have 4 ancestors that died in MO and the county claims they can not locate their death certificates. On one I was able to get a copy of a probate, but still no dc. That tells me they maybe misfiled, but with the increase in genealogy with the internet and county budgets being so tight I doubt the office staff has the time and resources to "go an extra mile" in looking for records. They do the best they can with the time and budget they have. I have even had the state of CA send me a letter that the state office of vital statics was too overwhelmed and understaffed to look up my record request in a timely manner and suggested I directly contact the county the record came from. No refund of the fee either as promised.
So don't forget to look for wills and probate court records.