I have studied Facebook API documentation and looked up other resources. It seems Facebook API does not provide a way to download stickers in a message thread. Is there any way I can retrieve stickers from Facebook threads?
If there is no way of downloading stickers available to developers, then my question is how is the Facebook messenger app able to do it?
As mentioned by WizKid (a FB employee) there is no public API available for getting stickers. The Facebook messenger app uses an internal API.