Dustfinger? What kind of a name was that? Meggie couldn't remember ever hearing it before, yet it sounded familiar, like a distant memory that wouldn't take shape properly. (1.25)
Maybe Meggie's memory of her early childhood isn't as blacked out as everyone assumes it is. Sure she doesn't remember her mom very well, and she doesn't remember the traumatic events that shaped her childhood when she was three, but some memories seem to be floating in her brain, waiting for her to trigger them.
The light from the hallway fell on her bed, mingling with the darkness of the night that seeped in through the window, and Meggie lay there waiting for the dark to disappear and take her fear of some evil menace away with it. Only later did she understand that evil had not appeared for the first time that night. It had just slunk back in again. (1.80)
Since Meggie doesn't remember the whole thing with her mom disappearing into Inkheart and characters coming out of it, she doesn't know at first that Dustfinger's appearance is not a totally new, random event. But later she realizes that it's part of a pattern that's been repeated in the past, and it's linked with very bad things to come.
"Sometimes it's a good thing we don't remember things half as well as books do. But for them we probably wouldn't know anything for very long. It would all be forgotten: the Trojan War, Columbus, Marco Polo, Shakespeare, all the amazing kings and gods of the past…" (5.8)
It's true, as Elinor points out, that books have long memories, much longer than people (because, when taken care of, books also live longer than people). And that can be both a good thing and a bad thing. Sometimes when something bad happens (like Meggie's mom disappearing, which Meggie hardly remembers) it can be good to have time erase it from your memory. But on the other hand, can you imagine what it'd be like to not have any of Shakespeare's plays?
How desperate the child looked—and lost. Elinor remembered the feeling. There was nothing worse. (8.1)
For all that Elinor and Meggie don't really get along at first, Elinor is strangely sympathetic. Then we learn a bit more about Elinor's past, like how her father neglected her and her siblings because he was totally obsessed with his books—so Elinor understands what it's like to feel lost and alone, abandoned even. Her memories provide her with plenty of material on that front.
So she hadn't run away after all. Did she like it in that other world? Did she still remember her daughter? Or were Meggie and Mo just a faded picture for her, too? Did she long to be back in her own world, just as Dustfinger did? (16.34)
Since Meggie doesn't really know her mom, she doesn't know whether her mom remembers her at all, or wants to be reunited with her. No offense, Megs, but you seem to have some abandonment issues (not that we can really blame you). It's not that she's overly attached the past like some people (ahem, Dustfinger), but instead because she doesn't know enough about the past to know her mom really did love her and didn't want to leave her.
A part of her was still in Capricorn's village, or trudging through thorns, or cowering in the ruined hovel and trembling as Basta came closer. (22.10)
And here Meggie learns the joys of traumatic experiences: no matter how much you'd like to forget them, sometimes you just can't. They burn themselves into your memory and replay, again and again, making it feel like the past is breathing into your ear.
"Tell me about her," she said quietly. "I don't mean the made-up stories you used to tell." (29.20)
Meggie learns the truth about her mother's disappearance and decides to ask about who her mother actually was, thus gaining insight into the past. Of course Meggie already had an idea about who her mom was based on all the fantastic stories Mo has told her about her mom being on a strange journey that's lasted nine years already—but a made-up past doesn't count as real… or does it?
"Capricorn… He has another name, too, of course, but even he doesn't remember it. He has called himself Capricorn since he was fifteen, after the star sign under which he was born." (34.37)
Fenoglio's insights into Capricorn's past are interesting, to say the least. Of course Capricorn has a background like most other people: mother, father, rough childhood, etc. But for Capricorn to reinvent himself so thoroughly that he doesn't even remember his birth name? Wow. That's pretty unusual. Gotta give it to Capricorn for being driven enough to reinvent his own past.
"Before you read, I want you to have a good look at my photographs… Do you see all those faces? Every one of those people made an enemy of Capricorn, and none of them was ever heard from again." (48.60-62)
Mortola has a bizarre and disturbing hobby: collecting photos of the people who get in Capricorn's way. If Capricorn doesn't have them killed, Mortola takes care of it behind the scenes. Hers is one dark and twisted way of remembering the past: memorializing all your enemies after their deaths.
The book at least would be his. It must be his. He would stroke the pages, and if he closed his eyes at the same time he would be home again. (58.5)
Dustfinger just can't seem to let go of the past. His memories of his own world motivate him to try to get his hands on the sole remaining copy of Inkheart, no matter the cost. And even if he can't be sent back, even if he's stuck in our world forever, simply touching the book that contains his old life in it will apparently be enough for him.