The mining world has been replaced with a brand new generated world in 1.8 and you should be able to get a lot more of the new resources that are available to bring home in the wilds.
Now know, if you didn’t get out of dodge like we forwarn y’all about this reset a long while ago. Then you’ll spawn at the server spawn and you may very well loose your inventory for the wilds, check to see if you did by visiting the wilds world as inventories are shared between the mining world and wilds. As well, any builds or chests that were left in the mining world are now forever archived in the world folder of the old mining world. If you’d like this world to be published for download to say recover something personal like a book, be sure ta raise your vote through the comments on this blog.
Also as with every world altering situation, please let us know if you’ve lost your inventory from the last three months. Anything before that is probably not recoverable.