There is no such thing as “confession by desire”. There is what’s called an Act of Perfect Contrition, but bad terms notwithstanding, God in his mercy can see the soul and the degree of his repentance, even without a priest available.
But the fact is, Hoess DID see a (Polish!) priest, who absolved him, AND gave him Communion. That tells us that in the priest’s judgment, Hoess’ contrition was sincere, and if his contrition was merely imperfect, the absolution took care of the rest. So we have a very visible sign of what is in all likelihood, a mass murderer being snatched from the jaws of hell to gain the eternal reward of heaven, not out of anything he did, but only out of God’s mercy.
Anyway, the reason I mention Hoess is because in discussions sin and God’s mercy, Hitler’s name is often brought up. Hitler showed no sign of repentance so anything involving him is mere speculation. But in terms of evil we DO have an example of an evil Nazi visibly saved, and in my opinion, Hoess’ story is more edifying (for those who aren’t too blinded by anger) than useless speculation about Hitler. Hoess’ story is the example of how a “monster” can still be saved in the end.