Is AUTHOR wrong in the post ? POST : (This is in the UK where tipping isn't an expected ot mandatory thing, but I like to anyway as someone who used to work in hospitatility and knows how nice an extra fiver can make you feel)

Partner and I were sat in a pub less than 10 mins from home watching the rugby last night. A few drinks in and knowing we're gunna be heading home and hungry soon I order pizza for delivery at 9:15pm. 

We leave the pub at 9pm and precisely 6 minutes into the walk home (I checked) and about a minute away from the house we get a call from my partners disabled mum asking us if we'd ordered pizza because the driver was at the door. She had been in bed due to having had a bad health week and was then quite irritated with us for the inconvenience.

Now I'm normally happy as larry if my food arrives at an earlier time than anticipated but this specifically bugged me, mainly because we'd ordered the food intentionally for this time instead of the general ASAP. As we walked up the path to my partners house the delivery lad was walking down and made a joke about how we should wait till we get home to order pizza.

AITA for a) not tipping him, and b) getting annoyed at the comment he made? 