Job offered to someone else while in negotiations?

I recently interviewed for a job, and they sent me an offer. I am married, and do not need medical/dental insurance so I asked if I could receive additional compensation in lieu of this. I was told by my contact that she would check and get back to me. I emailed her the next day- no response. So I called the following day, and was told that they don't offer additional compensation in lieu of medical/dental, but also that they'd offered the job to someone else who had accepted it. I had planned on accepting the position regardless of their response, and was taken aback by this. Has this ever happened to anyone else? That a potential employer withdrew the offer for employment without notifying you or responding to a negotiation? It just seems extremely unprofessional to me. I'm astounded.
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as scarce as employment is you are "astounded"?
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