I think it's been discussed on this forum before, but the online stock status for stores does not seem to be revealing the "whole story". Some Apple Store employees confirm the holding back of iPhone 6/6+ inventory for walk-ins, while others say "nay". All I can tell you is my experience. I was tired of waiting for a 6+ SG 128 I ordered on 9/12 from AT&T that wasn't looking like it would be delivered until the end of October. I got the in-stock notification for my local Apple Store from seaturtle.org. Before the store opened the stock status on that phone flipped between "in stock" and "out of stock" at least 5 times. I assume it was inventory being checked in, then snapped up by online orders. The store opens at 10:00 am. By 9:00 the stock status had switched and remained on "out of stock" for the rest of the day. I swung by the store anyway, just on a lark and they actually had a ton of the 6+ SG 128 on hand, but the website was still showing "out of stock". I canceled my pre-order on the way over, hoping they would have it in stock.
If your local store showed in-stock at any point in the morning, it might be worth a drive over to check in person.