You said "numerous players" have had this issue? You're kidding right? Seriously... why would you sell those things when they're NEEDED for such an important task? I mean, you could tell instantly it was important, and after the conversation with Siva, you'd know that you'd need those things again... And after performing all the ritual steps, the bowl would be on the ground. You really picked it up just to sell it when you saw that it's worth nothing?
If I'm being blunt, if by "more user-friendly game design" you meant you need the tooltips of the items to specifically tell you that, "DON"T SELL THESE CAUSE YOU'LL NEED THEM LATER"... I'm just gonna tell you that, this game is really, really not that kind of game. In fact, this game is not *user-friendly* at all, in that sense.
I'm just baffled, not trying to be a dick here. You can buy back anything you've sold, so just check at the vendors you frequently visit.