"Well I can hardly move on with my life without knowing he's alright, can I?"

"So you want me to find him before you'll give me the sail?"

"Before I will sell you the sail," he sniffs.

"Right."

Let's see, if she was holding a weird eskimo person prisoner in this town, where would she keep him? Shops, auction house, coffeeshop, docks...

...Unmarked building out on the edge by an old monument of some kind, which is not easily accessible or even noticeable from the main roads?

Ooh, promising. She'll go take a closer look. Casual-like.

There's a guy in a jumpsuit dancing in front of the monument. He keeps deciding to start the routine over five to ten seconds in. A little kid runs past, then another. A game of tag, apparently. None of these people object to her approaching that unmarked door.

Cool. It's probably locked?

Nope! Some jail, huh?

If it is a jail.

She'll go inside, then.

Well, there's a cell.

And a weird guy in it, muttering quietly while facing toward a corner.

"Are you the other northerner?"

"OH!" He turns around and jumps up and down. "Indeed I am! Hmmmm... I see the same green clothes and the same green hat. By the look of you, ma'am, would you by chance be... A fairy? Oh my, did you feel my telepathy? That's why you came to save me, isn't it!"

"...If I say yes, will you be quiet enough to not draw attention while I get you out of here?"

"Oh my, certainly! Tingle is my name and I will now patiently wait for your gracious assistance to bear fruit, kind fairy!"

Great.

It's probably too much to hope that the cell door is also unlocked.

It's not.

There's a torch on the wall, a chair outside the cell, and a bunch of clutter in the corner that might be hiding something.

Maybe there's a key in there somewhere. She checks.

No key. Yes switch, which when pressed swings the door open.

"Excellent work! Here is Tingle's heartfelt gift of thanks!" He does a little dance and produces confetti from somewhere. "Behold, the Tingle Tuner! Once I have consoled dear Zunari of his undoubtedly great but utterly unnecessary worries over me and moved on with my life as traveling merchant, you can use it to contact me at any time. I will offer a staggering variety of services in the future, with you as a special preferred customer of course. In fact, once I am united with my magic items you can purchase things at any time! I can receive rupees and send items through the tuner. How's that for convenience, Miss Fairy? Isn't it splendid?"

"Yeah. It is. Let's get you back to Zunari now."

"By all means, lead the way. I believe I will pretend to be a small creature of some sort, to deter suspicion..."

With a puff of green smoke, Tingle now appears to be a green rabbit.

Nice trick. Back to Zunari they go, then.

He doesn't recognize the rabbit until Tingle hops behind the stall and untransforms in a semi-hidden nook.

"Oh, my friend, you are alright!" 

They have a huddled conversation, and a tearful goodbye. Tingle hands Anna a sea chart that will apparently lead to "Tingle Tower," and runs off as a bunny again.

And then Zunari tells Anna, "Thank you very much for your assistance. I would sell you my sail now. Normally I would like to ask 200 rupees for it... But since you have done me such a favor, a discount is in order. How does 80 rupees sound?"

(She has more than enough, accumulated from where she keeps finding them randomly, and the goblins dropping them and so on)

"Okay!"

Here's some money.

"Oh, surely you have saved me today. Treasure it dearly! I am sure this is the finest sail in the world, please treat it as such!"

Here is: A boat sail, neatly folded, with an elegant swirly pattern printed on it.