Is it still stealing if it's an accident or Should I have empathy for big business?

I just accidentally stole a pair of shoes from Target. I was purchasing several things including a top, a pair of shoes, some food and scrap booking items. I was shooting the shit with the cashier, talking about the shirt I just bought, how she loves it and wears it all the time, paid the 30 dollars and walked out to my car.
"Wow," I thought to myself. "I never go into Target and spend 30 dollars. That's got to be a first. I can't think of a single time I've ever done that because usually I get trapped in all of the awesomeness that is Target and spend...wait...these shoes alone were 30 dollars."

Checked my receipt and sure enough - no shoes.

But wait people! As I sat here writing this I started thinking about the receipt and how it still didn't add up. She didn't charge me for a 15 dollar pack of scrap booking paper either.

At first I thought it might have been an accident, but it can't be. She couldn't have forgotten to ring up a pair of shoes and a big ass pack of paper but remembered to put them in a bag.

So, my ethical and moral alarms are ringing. Faintly. But they are ringing and I try not to ignore those. So, I sat for a second and thought if I should go back and pay for the shoes. (And now, the paper). I didn't. I don't really have the money to spend on them but I did make the decision to buy them anyway, and I was too busy chatting it up to realize that the amount she had told me to pay was less than half of what I was purchasing. It's not like she told me 30 dollars, and I thought to myself "that's not right, but I better not say anything at all". She said 30 dollars and I said "here is a 20 and here is a 10, good day ma'lady". (I'm paraphrasing).

So is this stealing if it's an accident?
Do you think check out lady, who's name tag read was "new team worker" or something like that, did it on purpose?
Should I even be torn over 45 dollars of merchandise that Target won't be receiving?

Thoughts, people. Thoughts.