I don’t think failing the ToK essay automatically makes you fail the IB… After all, your ToK grade comes from both the presentation and the essay, so unless you completely screwed up the presentation as well I think you’ll be fine. Based on the grade boundaries from May 2015, an E was 0-4 marks. Meaning, even if you get a 0 on the essay (which I can’t imagine is possible given that you actually submitted something), you’ll be fine as long as you got 5 marks or more on the presentation.
Lastly, you can still get the diploma even if you were to get an E in ToK (as long as you don’t also fail the EE), but you’ll need a minimum of 28 points instead of 24. But try to not stress out! Try to get your mind off of ToK and do something you enjoy! 
From an IB student currently struggling with his ToK essay 