if it has crystals and you are not getting high then maybe you developed a disease/immunity. because that makes no sense. THC gets people high....
The metabolic chain that leads to THC starts when geranyl pyrophosphate combines with olivetolic acid, in order to create cannabigerolic acid (CBGA). This carboxylic acid is the shared precursor of all the three major cannabinoids that can be found in the plant; THC, CBD and CBC.
Possibly he harvested prior to the precursor elements in the trichome heads even became CBGA that then would become THCA, CBDA and CBCA let alone becoming THC, CBD and CBC. Or maybe he harvested when there was CBGA but no THCA, CBDA or CBCA, let along THC, CBD and CBC.
If at least to the point of THCA, CBDA and CBCA he would get high because heat, as in the temperature of burning for smoking will cause complete decarboxylization and that would turn THCA into THC and CBDA into CBD and CBCA into CBC, along with doing the same for other cannabinoids, thus producing a high.
But it is likely that he harvested at or before the CBGA stage, and definitely not after .. or he would have gotten high.
Just because trichome heads exists does not mean THC and other cannabinoids exist.