A user may accidentally choose to hide a course that was showing on their current training, they may say things like my training is gone or it has disappeared. Hidden training is only hidden from the home page, it will still show on the user's transcript. From their transcript, they'll be able to locate the course name and resume the course. Once they do, it will add the training back to their 'Current Training' tile on their home page. 

I would be happy to assist you with locating your course again. Hidden courses are only 'hidden' from the 'Current Training' tile on the home page so you will still be able to locate the course by going to your 'Transcript' at the top of the page. Once you locate the course title, you will be able to resume the course from there and this will add the course back to your 'Current Training' tile on your home page.