I'm finding this thread strangely comforting, and hilarious.
I'm vegetarian, and in the early days of internet grocery shopping would have to be extra vigilant to avoid having meat and fish substitutes provided for my vegetarian slices, pies and sausages. I wasn't sure if the pickers were newly arrived foreigners who didn't understand why anyone would choose to be vegetarian, or if they were just bored and making their own entertainment.
Now that I know that a computer is providing the substitutions I can take it all a bit less personally. Razor blades for hamster bedding is my favourite so far, perhaps they thought the stubble could be collected and sewn into tiny pillows and mattresses?
I've found that the best way to get round that horrible feeling when you order 4 loaves of bread and get "no substitute available" is to order your four loaves from four different varieties of bread, and tick the box to say you want substitutions. That way, when one variety isn't available you still have a change of getting the other three loaves.
Same thing with eggs, after having no eggs at all delivered when the web page still had different sized eggs available I have changed from ordering 2 cartons of 12 large free range eggs, to asking for one carton of 12 large, and one carton of 12 medium sized free range eggs which seems to increase the chance of getting at least 12 eggs with the order.
Though since the Great Egg Shortage trauma I also add a couple of boxes of long life tofu, so that all is not lost on the breakfast scramble front if eggs are orf again.
I always phone the customer number on the invoice if I get something I didn't order, because I want them to know that the poor bugger also phoning to ask why they were charged for frozen cod in batter when it wasn't included in the delivery is telling the truth. Because when that happens to me I always feel guilty, as if they won't believe me and will think I am just trying to wriggle out of paying.