@mojala @petergleick @FediTips That is why they warn us not to completely block a server. As I understand it, when we choose to do this, all of the connections to followers we had on that server are erased.
I am unaware of any software to reverse this. It would probably need to run before the block anyway, keeping a backup of your followers for emergencies like this, probably stored in cookies. Maybe @FediTips knows of one.
If, as I suspect, you are stuck, I'd start following everyone I remember, posting about this, and tagging them. They can boost it and begin the process of reestablishing relationships through what were mutual followers.