Oddly, I've always assumed that Palpetine's statement was simply that. A statement.
I'd assumed he had no idea (nor concern) as to whether she was alive or dead but was simply spinning a tale to further bend Vader to his will.
That was my assumption as well. Recently, after seeing the last bit of the film again, it occurred to me that I may have been mistaken and that Anakin/Vader was directly responsible.
It got me thinking and so I decided to ask the rest of the forum (people who are more current on the lore and back history) to find out if the general impression was that Vader had inadvertently killed her and I was simply too thick headed to have picked it up the first time around.
The whole thing also raises other questions for me, but I'll mull those over in my head a bit before I waste anyones time.
