I'm just guessing here, Ezra, but I imagine the technical term for the "Private Investigator" that visited your parents place is a "process server" (ie a person who serves (delivers) legal papers in lawsuits, either as a profession or as a government official). And I am just guessing, but I imagine the reason he visited your folks on behalf of Giacomo Vigna* is because whois gives your folks' address in the contact information for your website.
As for the rest...well...I'm surprised you didn't portray the guy as flying in on bat wings and chewing the head off the family pet.
(Please let me know if anything in the above is incorrect.)
* Giacomo Vigna is a lawyer for the CHRC.