Wordpress无法识别我的自定义主题

I've been making a basic custom theme and everything was working fine. I had just finished pretty much styling everything in the blog section, left my computer for around 10 mins came back and it reverted back to the default twentyfourteen theme, claiming that my theme file was missing ('the template file'). I double checked and the file is still there so no idea what is going here?I've been making a basic custom theme and every