In Avengers #107 (by Steve Engelehart, Jim Starlin, George Tuska and Dave Cockrum), the Space Phantom and the Grim Reaper have teamed up. The Grim Reaper wants a human body for his "brother," the Vision and the Space Phantom captures Captain America so that his body can be used for the Vision to take over.
The Space Phantom had been working on this plan for a while, so we learn that back at Captain America #113, the Space Phantom captured Cap and Rick Jones and hypnotized them into forgetting that Cap's identity was now public and then brainwashed the world into forgetting it, as well. This was all to make Cap's body more useful for the Vision...
Don't wory, the Vision is just going along with it to stop them in the end.
What a weird retcon, but at least it DID explain how Cap could remain Steve Rogers after he had Steve Rogers killed off like he did.
Thanks to Fraser for the suggestion (and note, Fraser, that the retcon occurred all the way back at Cap #113, so technically Cap's identity was never out after that).
If anyone else has a suggestion for a future Abandoned an' Forsaked, drop me a line at email@example.com!