Plug underneath rear seat

Hello everyone, I've been on the forums for a while now but just barely signing up because I am looking at a 2021 TRD PRO that I might pull the trigger on. The place I am looking to possibly buy from have me a 24hr test drive and while looking over the truck at home I noticed one of the bolts that holds the driver's side rear seat in, was loose. Like finger loose. Upon inspecting closer, there appears to be a plug that is loose underneath the truck and I was hoping someone could help identify what this is. I'm thinking this should go into a sub woofer and the previous owner might have removed it? Can you help identify what this plug is? Thank you in advance.

 

Subwoofer

 

Yeah it appears it is missing. Found several options online if I search part number 861500C040. I'm guessing it just bolts in underneath there but I don't have any hardware at all.

 

https://ebay.us/m/4FG58u

Or facebook marketplace. Just a jbl sub.
Does your truck have jbl system? Wonder why you dont have the sub there. Previous owner took it out?

 

So I bought the truck. The dealer is going to replace the sub but yeah the previous owner took it out for some reason. I'm officially a Tundra owner.

 

Congrats and welcome

 

Thank you...I will be posting some pictures here soon!

Here it is!

 

Welcome to the forum.
The previous owner may have had some kind of aftermarket sub.

Good luck.

As previously stated, it is the sub plug.

 

Thank you.... Love your avatar also.