Animal Crossing New Leaf: I just got back from the island, where are my tools?

As I know, you can't bring your tools to the island. So that means you got them from the Gyroid on the island. They aren't your tools, you could only borrow them, (s)he would get them back when you go on a tour, or go back to your town.

There are two probable answers, along with some questions.

Have you checked your inventory? If not, do so.All your items should still be there. Next, if you don't know, the Gyroid at the island does not give the tools to you. They are only to borrow.This should explain why putting the rental tools into the drop-off box is impossible.

In conclusion, you probably misread the animal's statement.(but, you never really told us who you were speaking with..)