For further clarification the hole is along the LE pocket between the yoyo stop and the ULE fitting. I know it wasn't caused by a spar and I'm rather sure it wasn't bag related. I'm thinking Jim B must be right. Though I searched my flying field and couldn't find anything harder than grass out there.
@John, no other kites in the area.
@Kevin, didn't hear any big bangs.
Thanks for all the replies.
The cause is still a mystery to me.