The Mystery of the Missing Sunflower

This is what the most of the sunflowers in the garden look like right now. Beautiful bright yellow being explored be a swarm of big black  happy bees.  They are coming along nicely although not as huge as the ones that grew last year.  If all goes well I should be able to get a couple a bags of seeds out of these, but there is a problem.  The problem, besides me being able to take a properly focused photograph, is that something is eating or in some way destroying the freaking flowers.  Where are they going?  There is not a pile of flowers on the ground around these stems.  At least seven sunflower plants look the same way.  Right at where the flower would meet the stem it simply ends in a frayed mess.  Are they all going to disappear?  The only positive is that I think I could use these for make shift paint brushes for the kids to play with, but there gonna say "Hey Dad, where did the flowers go" and the best answer I got is maybe big foot at them.  Nature would be great if it wasn't for all the bugs and animals and stuff.