"Sabotage Building" mission can only be performed when the target city has a monument. (not a stele, an obelisk, a totem pole, nor a free monument from Stonehenge)

Savefile:
http://forums.civfanatics.com/attachment.php?attachmentid=165257&d=1196972752

I was about to write a bug report on this, but it seems its already observed.
Indeed, after destroying the monument, the sabotage building mission is no longer available. So for now, don't touch the monuments. I hope this bug will be noticed by someone in the power to fix it.