Not all records are on Findmypast and even if the parish is covered there are sometimes date gaps where the records have not yet been loaded on to the site.
If any of the parishes you need to check are not in the Members' Area or on Findmypast then you would need to visit Tree House in Exeter, Devon Archives & Local Studies in Exeter or Plymouth & West Devon Records Office as they all have copies of the parish records assuming they have survived and been deposited with one of the Records Office. Any registers deposited with a Records Office in the last few years would not have been filmed but they should hold the original registers. Both Record Offices have listings on their site of the Registers they hold.
Check to see if there are any Civil Cemeteries open in the area at this period. Could they have been Non-Conformists and therefore buried in a Chapel Cemetery.
If John or Susan were not born in Loddiswell it's possible the burial took place in the parish they originally came from.