yea, I get that..on the hard way ツ
I switched to getRootByName in my extension
but it wasn't documented anywhere
btw. id's are not consistent...they are changed when adding new nodes (folders/bookmarks)
Chrome doesn't behave like that
BB is first child, other bookmarks is second (0 & 1). Everything else falls into those two.
In Opera other "major" roots switch their id's when something is added