Not very neighborly

Had such a discouraging experience in the grocery store today.

A woman pushed my cart out of the checkout line while I went to get something.  When I got back, like 2 minutes later, she said "Oh no, you get in the back of the line," and then said she didn't "see" my cart.

I wouldn't have gone if there wasn't plenty of time before I would be putting my items on the belt. And I said to the woman in front of me, "I'll be right back" (not that I would expect her to look out for me and save my place, but damn!) The woman who took my place hadn't even started unloading her cart yet. I wasn't too surprised that she took my place, but I was surprised that she was so nasty to me, and that she basically lied. If she had said "you weren't here, so I went ahead" that would have been quite reasonable and understandable. But she was super nasty about the whole thing, like the supermarket line is some life or death situation, like she's the Line Cop, making sure no one gets away with anything (because I didn't affect her at all - it's not like I tried to get in front of her when I got back!)

It's a neighborhood store, for crying out loud. For all she knows, I live on her block. How could someone treat their neighbor that way???  I think people were nicer in the big city where I used to live than they are here in the 'burbs, despite reputations to the contrary.

Kind of sucked the life out of me.  I'm feeling so stressed and have so much on my mind, and I was just so taken aback to be treated that way.  Why so mean?  How can that possibly be necessary?

ADDENDUM

I got screwed out of line again on Wednesday - I picked out a dress at Macy's, and went to the counter, but the clerk wasn't there.  I left the dress on the counter and stepped across the aisle to hang up the dress I wasn't getting.  As I walked back across the aisle, another woman hustled up to the counter, just as the clerk returned.  I was willing to wait rather than say something (my second mistake!), so I just reached around the woman to retrieve my dress (thinking, naively, that the clerk or the woman might acknowledge that I was obviously first).  The woman then required an obscene amount of time, checking on a discount and looking up her account information.  I finally gave up and left.  Super annoying, though no one was nasty to me this time!