FBI will retrieve the seed online when it's installing CIAs that need it if it has an Internet connection. The seed is needed to decrypt the games downloaded/installed from the eShop. freeShop and CIAngel retrieve the seed for you when they install the game. If you made a backup of these games using something like GodMode9, you would need the seed if you install it on a system that never installed the game. You can get around this by decrypting the game with GodMode9 or on a PC, etc. That's why you'll see games that are decrypted online. I think that's also needed for Citra, but since I don't use it, I'm not 100% sure. The seed was introduce in firmware 9.6 if I'm not mistaken.
If you had Internet connection when you installed those games, FBI would have retrieved the seed for you without any input from you. It could also have been a cartridge dump which don't need the seed or someone might have decrypted the CIA already.
Once you got the seed, it's there unless you delete it.