
Quoting
bam!
That crap happens all the time. Cashiering is monotonous and cashiers sometimes bag up merchandise and say "thank you come again". Especially if the customer swipes a card and it doesn't register, a bored cashier can think payment went through.
The real question is...were the items scanned through the POS system? IE did you actually ring up the items and forget to take payment or did you just put the stuff in a bag?