I lost a t-shirt I bought on Saturday, I was so knackered by the end of that day when I bought it that I don't remember even picking it up at all and when I went back to the guy I got it from on the Sunday he said he definitely gave it to me so I must've dropped it somewhere.

The t-shirt was supposed to be a present for my brother so I had to buy him a new one and when I got home and gave it to him he decided it was too big - even though I thought it looked fine.
I also managed to drop some change on the floor and not close my purse properly so that all the change I had ended-up at the bottom of my bag.
Loads of things I bought I found cheaper on other stalls - some things were quite significantly cheaper.
I went down a busy isle, got bumped into, rebounded and bumped into someone wearing a blue fox costume quite hard - I apologised but still felt really bad about it.
I bought too much and had to buy two of those big expensive sturdy shopping-bag things to take it all back in and had to carry them back on the underground, train and bus home and when I was waiting for the bus I had half-an-hour to wait with a really religious man going on and on.
Could've been worse though, at least the t-shirt I lost wasn't that expensive and I bought some great things, used the underground for the first time without getting lost and met Craig Charles.