So what you are saying is that I should shrug my shoulders accept her shit behaviour at her dropping the bag on the floor and walking away.
Well the most obvious "thing to do" would be to say something at the time - but I'm guessing you didn't.
So instead you are fuming all day and looking for others to fume with you.
It was just rudeness - and maybe she is a dreadful person, rude to all who encounter her, maybe she was having a bad day, maybe she just found out her zero hours contract was being cut, maybe she didn't like the look of you? Who knows?
Point is, she was a bit rude. She wasn't even very rude. Sports Direct pull things down with poles all the time - what upset you is she just left it in front of you, rather thank bending over herself and passing it to you. So a bit rude, not extremely rude. One of the least rude rude things I've read about on MN and MN love rolling eyes at "Rude". Rude is the new Smug.
Really if you didn't want to accept her behavior you would have done something in the shop at the time. Or you can do what lots of people do and decide not to shop there again.
How is starting a thread about it on MN to share your fumes doing anything about it?