Good question, seeing as we are the only ones to have used them; depending on whom you believe, one is still missing from the event the questioner describes; and that some bloggers (including this one) have warned against something like this, to be blamed on them.
"Before lecturing Pakistan on our nuclear safeguards, maybe the US government might want to check its own backyard:
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Of course, Pakistan sure seems ripe for the blame lately (as they surge in my poll).