I wouldn't say it's missing "intentionally"; I'd say it's missing because in this dialogue on friendship, it isn't necessary to repeat the word for "friend." Obviously the sentence, in its context, refers to friendship, and quicum refers to a friend. If you take the sentence out of its context and do it in Greek, you need some sort of referent for ᾧ with ἔχειν. And you've found it (at least an indefinite referent) with ὅτῳ (= ᾧ τινι, i.e. τινα ᾧ). Good work!