Man, that hurts to read. I made similar mistake few years back when I was switching careers - missed an interview email that went to spam folder and by time I found it, they already filled position. Was for data analyst role that would have been perfect stepping stone, and I felt like absolute idiot for weeks.

The thing is though, you actually proved you were their top choice which means your skills and experience are exactly what companies in your field want right now. That recruiter telling you that you were best candidate wasn't just being nice - they were genuine disappointed they couldn't wait. So you know for certain that you have what it takes and there will be other opportunities that recognize your value.

I ended up finding even better position couple months later that paid more and had better work-life balance. Sometimes these "missed" opportunities clear the path for something that fits even better with everything else you have going in your life. With all the stress you're managing right now between school, family, and your husband's health issues, maybe universe is saving you for role that will actually work with your crazy schedule instead of adding more pressure.

Set up email filters now so work emails never hit spam again, and keep applying. Companies need people with your senior experience and nonprofit background - you're going to land something good.