...I blast her once more, and instead of flying into the air, she simply vanishes. I tried waiting, in case she fell elsehwere and got knocked out. I tried fast travelling, to see if she would spawn next to me. No luck. After scowering the entire lake bed on foot, I turned up nothing.
What do you think happened? Did my explosion rip a hole in the fabric of reality, absorbing Cass forever? I had to reload, of course. C4 is an expensive resource. Cass, however, is expendable.