If you make an object in inkscape insensitive how do you make it back into sensitive again? I am unable to figure this out.

If you want to undo it immediately, Ctrl+Z will do it.

If you want to unlock some locked object later, currently you'll need to reach it by Find (with "ignore locked" disabled) or by XML editor. Later we'll add a command like "Unlock all in layer" which will unlock all objects in the current layer. Granted, this is not very elegant still. This is why making objects locked is rarely the best way to handle locking. Instead, move the object(s) to a layer and lock the layer. This is much more convenient because you can always select the layer in the list.