Anyhow, I normally create all of my labels on project A but somehow earlier this week, I created a label on project B instead. I can view history of project A and see exactly where the label SHOULD have been, but I can't find a way to insert a label on project A at that point in the past.
Do a history query on $/A ( Change to option to View folder history by version ). Find the version of the folder for A within the History Explorer, and then click Label.