That's why I made "indicators" plural, because it should be one of several factors to take into consideration, not the end-all-be-all answer to the question of whether a female is a virgin or not.
And as far as not all women being born with a hymen, that's definitely not the norm. I just looked it up and read a few conflicting claims, but suffice it to say having no hymen present at all is a statistically very, very unlikely. There is such a thing as an imperforate hymen, and not all hymens look the same, so it can be mislabeled as absent or damaged or whatever.
As to the question of the Islamic state of affairs… The whole Islamic world is not homogeneous. Heck, this discussion could be applied to most of Africa and Asia as well. The Arab Spring is a good example of the folks over there getting fed up with the status quo. Sure, they do have a lot of socially/culturally unsustainable views and norms, but it's far from static. The region has and is changing.