Leftovers at Kelp?

Okay- so I had this great idea that I was gonna try to get leftovers at Kelp so that I could restock food items.

I used jn's tips to get leftovers- basically taking my lightest pet, feeding her until she's very bloated before taking her to Kelp. It also said it helps to buy one thing off of each menu- which I did.

What went wrong? I didn't come back with any leftovers and lost ~65k np...

Maybe I got too greedy wanting to make big bucks :'(

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I'm not angry that I lost np because I kinda figured it wouldn't make sense to get leftovers so easily (because then everyone would just go to Kelp and restock their food), but I'm wondering if any of y'all restock Kelp foods? Some food there is worth 1 mil which was what I was hoping to go for.