chocobo whistle

[-DMR-]

Don't know what happened, but I was out in La Noscea, outside Limsa Lominsa, but when I used it for the first time, nothing happened (the icon is now greyed out), and I can't obtain it again. Is there such thing as a lost and found npc?

[Orophin]

Go to your General Actions and Traits menu, look under Mounts, drag it to your hotbar.

[Sagittarian]

You also can't summon your mount inside cities.

[Nutz]

All mounts and minions are like that. The item you use unlocks the ability to use them. I imagine it's set up like this because several minions (and perhaps current or future mounts, never looked really) can be sold, so there needs to be a usable item for them.

[-DMR-]

Am I right in thinking the whistle itself can be used just once, but I can continue to summon and mount the chocobo? I know it'll need to be outside the city state areas and away from danger

[Ceaulieignemortel]

Yeah that's right

[Umo]

Just think about mounts and minions as spells you learn via usable items. Once you have used that item, just open the Action & Skills menu, locate the mount/minion icon and drag & drop it to your hotbar.
On the other hand, there are bardings for your chocobo (not for other mounts you may acquire) which are usable items aswell and once used you have to manage them through Companion menu.