Right. If one lives in an area prone to malaria, has good immune system, will the body tend to carry the antibodies all the time?
The pedantic answer is "yes".
The pragmatic answer is "if only it was that easy" -
https://en.wikipedia.org/wiki/Malaria#Immune_system_evasion
https://en.wikipedia.org/wiki/File:Global_malaria_deaths_201...
Yes, which is why the immunological tests done in 2006 were not seen as conclusive. However, this time they found actual plasmodium DNA which suggests active infection at time of death. Including from two species, suggesting double infection. Fun.