You two brought up the most important DH point. This is the point that also makes DH fall apart, lacking support. (not sure if that's a good thing or a bad thing -- probably bad, b/c I'd've liked DH to be a story I could hold onto. But, alas. It seemed to fall apart like Voldy at the end of the DH2 movie. ;_;).
It seemed very strange to me that Snape would tell Harry what he had to via memories, even though there is a risk that Harry would not be able to gather them in time and they would be lost. The other point, is the one you made (YaY!) -- what if someone got to Snape before he had a chance to tell Harry?
And DH doesn't give an answer to it at all -- it just assumes that, somehow, the story goes from A to B to C, pulling the plot along, but doesn't explain how this happens. Just that it does. I think most people would call it a plot hole, but instead I rambled on for three small paragraphs explaining all around it without giving it a definite term. (Sorry 'bou 'tha.).
Heh heh heh. I just thought of something. In theory DH works. ;) Heh heh heh heh heh Get it? In Theory? ;) (Bet you Snape'd be able to make DH work practically, as well.^^)
Hooray! for a nice long fic for the Fix-It-Fest! (The longer it is, the more fun slow-reading it is.^^)