Thermostat install?

I am taking apart the upper and lower to figure out where the coolant leak is coming from. When I took the water neck off the termostat fell right out. I was reading in the my book that some T-stats have locking ears that you turn to lock it in place and the some have a spring like flange that holds it in place. Mine has niether, not does it have a bleeder hole and I don't see anything in or on the lower and water neck that would hold it there, just an inset on the water neck. Since I have a GT-40 lower is that gone now, or how does it lock into place, especially to re-install it? It looks like the old one was RTVed up to stay but has since came free.

Also does the spring side of the T-stat go into the lower or the other side. it fell out so fast I did get to see how it was oriented.

Thanks and sorry for the trivial question.
 
There's nothing to hold the thermostat in place, except the fact it's obviously sandwiched between the block and the thermostat housing. :D

Seriously though, I think I usually put some rtv on the gasket surface that goes against the intake. Then I set the thermostat in there and set the rtv'd gasket over it, and that will hold it in place while you put the housing on. I think I always put rtv on both sides of the gasket. Not a lot, just a thin layer.

Jeff