Hard to say from that angle, but I'm leaning towards leaf ... If it is a leaf, you should be able to see the "seam" where the two leaf edges meet. If there's no seam, it's a sheath
That's where I get confused, because at this point the seam has usually split to reveal it as a leaf. The fact that its still closed, as well as noticeably "plump" to the touch, makes me wonder... Here's hoping!