Surely you'd expect there to be lots of civilisations at different stages, not just one that is ignoring us and hiding.
The idea that there are only two civilisations in the universe is far less likely than there being just one in my opinion.
Also, although it is probably unwise to extrapolate too much from ourselves, any civilisation is likely to be made up of beings that either evolved via natural selection, or were designed by beings that evolved. As such they are likely to have a sense of morality, as we do, and to be interested in the welfare of other creatures, as we are.
I don't think a civilisation that could mine stars would just hide from everyone else.