I had the same experience, I played through the temple after the Vale and I couldn't remember it at all. "Wait, is this new?" "I thought Dragons Eye came after the Vale..."
I was looking at the screen shots before I bought the game and most of them I couldn't even remember seeing before. And when I started playing the game, I didn't even remember all those little events around Easthaven until I uncovered them again. I certainly didn't remember all those Orcs in the first cave outside of town. Ouch! And right now I really have no idea what to expect once I get into the game more, unlike the BG games, which I've played off and on a few times over the years. It's a nice feeling frankly. "Everything old becomes new again."
Yeah I remembered very little from this game because I never played it again once IWD2 came out. About all I really remembered was 'There was a dungeon that looked like a hand.' (Which I've just entered, coincidentally)
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I can retain almost everything as long as I eject some unimportant info (like birthdays, work deadlines and bills)