So sorry Gage, that is awful to wait and be so disappointed. Don't blame yourself, you obviously intended the best for your mare so there is nothing to feel shameful about. People miss these things, you're not alone.
Foaling out mares isn't easy, and especially when you haven't had experience with them, mares can completely fool you when it comes time for them to give birth (and even we experienced ones still get fooled now and then!) What a bummer to lose your first baby! Email me ok?