So let me see if I understand.
With a haversack, I use the Quick Draw feat to pull out alchemist fire flasks, which NORMALLY lets me pull 'em out at full BAB, but with the haversack limits me because while I can draw as a free action, I have to wait for the retrieval (which I would think would be implied by a draw, but whatever). End result, even if I have the Quick Draw, the haversack prevents me from drawing at full BAB.
However, with a normal backpack/pouch/other storage device, I use Quick Draw to draw at full BAB and it works? Because they don't have a "retrieval" time?
If normal storage does have a retrieval time, then Quick Draw is a failure of a feat, as it specifically says you can get full BAB for thrown weapons, yet anything apparently defeats it.
If normal storage does not have a retrieval time, then the haversack is a failure of a magic item, as its supposed advantage over normal packs is in fact a disadvantage.
Where in the rules does it specify that draw and retrieval are separate, anyway? I want to read that for myself. Is it like a stacking rule? How do they stack?
EDIT: Hmm. I see it. Page 141 of Players Handbook. The problem with this is that a flask is in a weird space of being a weapon you draw and being a stored item. Apparently it comes down to context -- if the storage device lends itself to Quick Draw, then Quick Draw applies. If not, then it's a rummaging-in-the-pack retrieval issue. I guess in such a case, the only good option for a halfling thrower is to buy the bandolier. At least there is SOME option that works.