I work in our local Sainsburys, and I must ID up to 30 people a shift.
Our policy is if you APPEAR to be under 25, you must PROOVE you are over 18. If you are buying alcohol and come into the shop with someone else (a friend etc) you must BOTH have ID if one of you looks under 25. The implications for us, as staff, are huge if we sell to someone underage. £2000 fine, loss of job and a 2 year criminal record.
I have been "stung" by three trading standard test purchases in the last month. A youngestr comes in, and routinely looks 21/22 +, and either tries to buy alcohol, or cigarettes, a lighter, rizlas, tobacco, paracetamol, etc. I request ID, they say something along the lines of "sorry it's in the car/in my other bag/my other trousers". I then ask their age. TS Test Puhasers are NOT ALLOWED to lie to you they must tell you their age, and these three, without fail, have all grinned at me and said "17 - well done love".
Now, I don't care how old you SAY you are...I work in a minumum wage job to earn extras for my kids...I WILL NOT get myself a criminal record and massive fine because of the fact that you don't want to cary ID.
I have common sense...anyone with a child under 12 I don't refuse to serve them because of the child, UNLESS the child has picked up and brought alcohol to the checkout...in that case I do refuse. A group of teenagers, sorry you ALL need ID. Often towards the end of the night as they are queueing up, they see me eyeing them up as I serve a customer and the banter starts..."she's gonna ID us get your stuff ready lads" . I had a 13 year old lad the other week take a bottle of carlsberg to his mum..."mum can I have" "ok" she says, and puts it in her basket. Sorry, but no. She was clearly over 25, yet I refused the sale...she was buying it for a minor. Not on my shift, she isn't.
I'm polite, I explain and I apologise if I refuse a sale. 90% of refused customers are ok about it. The other 10% end up with manager involvement (who ALWAYS back me up) or 999 involvement whenthey get violent. Around twice a week usually...it's like working on the Shameless estate at that shop.
And you know what...the younger the customer, the twattier they are about being refused.
OP, I think you behaved very childishly leaving your shopping, but I think the checkout girl could have been politer to you.