Can someone have acute kidney failure, not know it and die? or would it eventually get severe enough to where they'd know they need to seek help?

Acute = fast: Acute renal failure can act fast and as it gets severe you'd most likely know about it and seek help, but possibly not soon enough to reverse the condition. Similarly, the problem with chronic renal failure is that you may not catch it early enough to reverse or delay the progression of the disease. Testing can be pretty simple & good treatments frequently are effective so get checked by your doc.