Okay so I may have done something dumb, but I finished the game and then save my file.  I play it again using that save file after beating the game to collect last few missing items, such as the Mirror Shield and to finish up the heart container quest.  So I'm buying the last figurine from the shop (shell quest) and I just happen to get all but number 6, so basically 131-136 which only appears after you finish the game were completed prior to me getting the number 6 piece.  Long story short, I got the gold medal from the figurine guy, but never the key to his house to collect that last heart piece I'm missing...sucks, but I don't know a way to get that key now, the guy keeps congratulating me for obtaining all 136 pieces. 

Thanks for any help, or you can laugh at my misfortune.  Can't wait for that Link between Worlds to come out...

I don't recall for sure, but I think there are a few missable characters, and as such, missable figurines. It's been awhile since I looked it up, but a couple of kinstone trades disappear once you reach the final section of the game, and due to them, you can miss a character or two.