Guild Wars 2

So I noticed a lot of runes not having actual crafting recipes (i.e. the ones mentioned in the title).
Could anyone provide a bit of insight as to how these runes would be obtained?

Salvaging armor drops

There are a large number of runes (and sigils) that can only be obtained by salvaging them from armor/drops. For example, all runes relating to a race’s capital city (e.g. Black Citadel, Grove, Rata Sum) cannot be crafted. Tier 3 Cultural armors come with a Superior version of the rune already installed, but lesser versions must be salvaged from drops.

In addition, there are also runes/sigils which can be only obtained by trading them for tokens from Dungeon Vendors. These runes are account-bound on acquire, I believe, so you won’t see them on the TP either.

They are from random drops, as stated before. You will not be able to assemble a full set from your own random drops. Go to the trading post and either buy the individual runes (safe way) or purchase armor with the runes installed and use a salvaging kit to get the runes out (riskier, don’t do this with anything but mystic or black lion kits or it will not be worth it).