Where is the battery??? 1996 Chevy/Grumman Olsen Step Van

This is my first post here - I hope this is the right area for this question.

The battery on my step van just died (I left the lights on). I went to charge it up... and I can't find it.  Its not visible lifting the hood and peering at all angles.  I found all the fuses, and traced the lines as best I could.  I can't see any mysterious black boxes it could be hiding within (the only such box seems to house the a/c).  I crawled under and looked around.  I lifted the cover in the cab area, directly over the engine. I even lifted the floor plate directly over the transmission.  I think I've accounted for every cubic inch of space in those compartments.

I considered it might be stolen, but I can't find an brackets or support platform for the battery, nor any dangling wires.  Everything is so dirty, if something was removed, I think the clean spots left would be obvious.

Does anyone know where battery is hidden on a 1996 Chevy/Grumman Olsen Step Van?  

Problem solved - I got the answer on another board.  But in case anyone has the same problem:

My battery turned out to be very small, and tucked into an too-small-seeming space under another floor plate, directly beneath the drivers seat - next to the plate over the transmission I had already been looking under.