Any advice would be greatly appreciated!!

I left my slider window in the back of my truck behind the back seats slighly open during several days of rain (I was away)
now I have water sloshing around in that back panel. I cannot for the life of me find where to drain it from. I've exhausted youtube and I was under there....cannot find the plug to drain it

Any ideas? thank you in advance for any advice

 

You may need to remove the seats to gain access to the bottom of the area, but you might be able to drill a small hole near that bottom and allow the water to drain out.
A 1/8 size drill carefully used would be all you need, just don't go deep because you could drill through the ares to the outside then it might drain out there , but now you created a place for rust to begin. That metal is not that thick so if you are successful just put a small short sheet metal screw with some sealer in the hole when done

 

I never thought to go at it from inside so that's a good thought.
And I did see an area where I thought there should be a plug so I will try that...GREAT idea about putting the screw in the hole
Thanks!!