Absolutely, if pursued with intent, they'll be very evident. That doesn't necessarily mean you can do anything (inside the protocol) against them. The orphaned chain could be the victim of a 51% attack – or a failed attempt at a 51% attack, or an inadvertent side-effect of network lags. But by design, to converge on a shared serialized history, nodes eventually trust the longest chain as the winner-as-chosen-by-hashpower.

To have nodes consensually adopt some other chain, you'd need some other nice converging criteria for preferring a shorter chain. Those are hard without adopting some other centralizable or monopolizable authority role (like trusted timestamping).