Somehow I have deleted all of my categories. The items remain, and still have the category name by them, but the categories are all gone.

I was deleting my trashed items, then I thought I would have to delete my trashed categories afterwards. But I've only gone and deleted the categories that had stuff in them instead.

There were loads too!

Any ideas how this happened, you never used to be able to do it?

EDIT: Sorry today with a clear head they are in trashed categories. Phew. Begin dumb :|