From their website I gave you above, it looks as if the Cememery Friends have photographed and transcribed every grave, so if the people you want aren't in their Memorial Inscriptions list, I'm afraid you're out of luck.
If you have plot numbers, you can double-check on the maps, where graves are annotated with names (presumably from the headstones). However (a) there doesn't seem to be an index to which subsection map contains a particular numbered grave, so you have to try them all, and (b) I noticed some gaps between the the subsection maps where whole rows of graves aren't shown, and just possibly weren't transcribed or photographed.
Guy is, of course, correct about it being possible to consecrate graves individually, but the QR registers have a "Consecrated?" column which would say whether this had been done in the cases in question.