Si is the brother of Duck Commander Phil Robertson. Si is a Viet Nam veteran, and uncle to Phil and Miss Kay's four sons. Si works as the reed man at Duck Commander, making the reeds that go into every duck call. Si is known for his storytelling, and his constant use of the expressions "Hey!" and "Jack", (which ends many of his sentences). And for his ever-present tupperware cup, ever-filled with iced tea.
Si says, "Yo beard is so fat, not even Dora can explore it!"
The cache is placed along the road allowance. There is no need to trespass on private property.
Uncle Si may or may not be holding a clue to the series final: the Duck Commander.
Congratulations to Foam Follower for FTF