There used to be a very simple mechanism for protecting works to become orphaned: authors registered them with the Library of Congress. This also ensured that the work eventually could enter the public domain.
It was greedy European publishers that killed this, and then forced the US to comply. And now they are using orphan works legislation to enrich themselves; if you look at the European proposals for orphan works, they want to charge for the reproduction of such works and then redistribute the money to current publishers and authors. That is not how orphan works are supposed to work.
We should bring back mandatory copyright registration; it's the only sensible way of dealing with orphan works and the public domain.