How can I un-deface someone on Facebook?
Going forward, maybe it's time for a greasemonkey script to hide the unfriending feature. Use "hide" feature going forward.
You will have to ask that person to forgive your clumsiness and be your friend again. Once they are deleted, they are gone!! Next time be more careful with who you are deleting. :)~
It isn't possible. Send that person a friend request again and explain the situation. Say that you are sorry and that it was a mistake.