Pinning and unpinning a friend on Snapchat is pretty easy. I'm sure you must have unknowingly pinned someone, and now you want a way to unpin. Not to worry, all you need to do is open Snapchat and tap the speech bubble icon at the bottom to open your Chat screen. Long-press the pinned conversation. A menu will pop open; tap Chat Settings and select Unpin Conversation.
To unpin anyone on Snapchat, go to your Chat screen and press and hold on their name at the top of your list. When the menu pops up, tap on Chat Settings, then select Unpin Conversation. The chat will immediately drop back into its normal chronological order!