If you have a Parent version and Child version and a feature was deleted in the Child version, whether it is lost depends on whether it was a new feature that was added using the Child version or whether it was an existing feature in the Parent version, right? If it was an existing feature, then it should still be in the parent version, and when you reconcile/post, can't you manually review that edit and favor the Parent version?
As for backups, we have a nightly backup in SQL Server. But that means I'm willing to lose a day's worth of edits.
We set default to protected and make our child versions public. But that also means that we have to pay attention to what we are reconciling and posting to default.
If you have already reconciled and posted the deleted feature in the child version to the parent version (sde.default), you're done, it's gone. Unless you haven't synchronized changes in your replica, then that feature would still be in your replicated geodatabase (hopefully).