No, they don't return to the Corp's hand. It's just worded poorly.
That is what I suspect is the case. Do you have something to back it up with, like an official ruling/FAQ, a judging at the gencon tournament or some such?
Further down on page 18, under "Concluding the Run":
"After the Runner has accessed all required cards, he returns any cards not stolen or trashed to their original play states. For example, an unrezzed card in a remote server returns facedown to that server, and a card accessed from HQ returns to HQ."
If you read over the rules for accessing the Archives, you might also get confused as to what you do with any upgrades if this part weren't in there. In fact, if you read that part, and then the multi-access rule, you might find accessing the Archives to be rather daunting.
It just comes down to the fact that the rulebook was not written as well as it could (or perhaps should) have been.