The ECU is held in place under the seat with a big rubber band. When I was just
looking under there, I found another rubber band just lying in there, and I don't
know where it goes. I was in there just a couple of months ago... it wasn't
loose in there then. Maybe you could look under there and see if you can tell
where it goes?
The extra clutter you see under there is that I got that over-priced Honda
accessory connector (fancy cigarette lighter) and I got a splitter for it
to run a GPS and the relay for my heated gear.

-Mike