Check for adjacency after or before using a moving tile?

Question

I'm white player and I draw a desert card.

I place my three settlements there:

Now I use my special ability to move any settlement to a desert field:

I choose the settlement on the right:

Now my question is: Can I place this settlement on a different desert terrain OR do I have to place it on the same place where I took it from?

I haven't built on (or next to) any other desert fields yet. So the only adjacent desert field would be that one.

Answer 1

The answer to your question, as asked, is "The settlement must go back to where you picked it up from."

But your question includes this phrase

I haven't built on any other desert fields yet. So the only neighbouring desert field would be that one.

This is not the correct rule. Perhaps you meant to say that you haven't built on or next to any other desert fields. If you've built next to other desert fields, then your settlement could be moved to a desert field next to those settlements.

Answer 2

In the BoardGameGeek FAQ it says:

Harbor and Barn: Adjacency is checked when placing the piece

Check for eligible hexes after picking up the settlement to move. E.g. if you place 3 settlements together on 3 canyon hexes and now have no settlements adjacent to any canyon hexes, and then you pick up one of those settlements with the Barn, then you have to put the settlement right back on the hex it came from, since that is an empty canyon hex next to one of your settlements.

It links to a thread where the game designer confirmed it:

Moving a piece means picking it up and then placing it. Adjacency is checked when placing the piece, which is after removing it.

So, no, you can't place this settlement on a different desert terrain. You have to place it on the very same field you took it from.