Vanishing Wonder

[Abaxial]

So I was building Jebel Barkal, when after a fair few turns it just vanished from production and I was prompted to produce something new. Last build was given as Temple. Jebel Barkal also vanished from the list of Wonders available to build. But there was no message it was built by anyone else, the list of previously built wonders doesn't mention Jebel Barkal and there was no recovery of anything for the wasted production. I wonder if this is because Jebel Barkal was not one of the original Wonders, and the code that handles other civs building it doesn't recognise it?