Another example would be Draco, to Harry, in Chapter 7:

"The courts use Veritaserum, but it's a joke really, you just Obliviate yourself before you testify and then claim the other person was Memory-Charmed with a false memory. If you've got a Pensieve, and we do, you can even get the memory back afterward."

And that's a very good point. I can't quite tell whether Dumbledore picked up on the mistake that Lucius made, just from Harry's memory - the only reaction we are directly told about is

Dumbledore's face had grown more remote as Harry went on, and at the end there was a look of ancientness about him, a sternness in the air.

"Well," said Dumbledore. "I suggest you take the best of care that the heir of Malfoy does not come to harm, then. And I will do the same." The Headmaster was frowning, his fingers drumming soundlessly through the inky black surface of a plate inscribed with the word Leliel. "And I think it would be most extremely wise for you to avoid all interaction with Lord Malfoy henceforth."

and then the conversation switches tracks. If Dumbledore did get the subtext just from Harry's (described, offscreen) verbal recollections, then the lack is just a minor puzzling detail; but if he didn't, when he most certainly could have from the inhumanly perfect reproduction of a Pensieve, failing to use one seems a critical flaw.