Yep, for The Moose you can't use cover to hide, otherwise the achievement won't pop. You'll have to go oldschool and just sort of stand behind the buildings/cars and hope she doesn't spot you, haha.
Anyways...just saw the updated achievement list, sorta miffed that my completion status has been KOed so early, like when a buddy and I 100%ed Resident Evil 5 together and right afterwards the Versus DLC came out, haha. Still looks like an easy list, and I kept the game around for the DLC cases knowing they'd have achievements so it's no big deal I suppose.
100% retail - Lego Batman, Lego Harry Potter Years 1-4, Lego Star Wars TCS, Batman Arkham Asylum, The Godfather (1250), Resident Evil 5 (1000), Oblivion (1250), Dynasty Warriors 6 Empires, Fallout 3 (1550), Avatar TLA, Marvel UA, Marvel UA 2 (1000), Left 4 Dead (1225), Assassin's Creed 1+2, Sega Megadrive UC, L.A. Noire (1200), The Saboteur
100% arcade - Gunstar Heroes, Pacman CE DX, SSF2T HDR, The Dishwasher Dead Samurai, DR2 Case Zero, Banjo Kazooie, Dash of Destruction