I think these are all great ideas.I think that she was not sure that you would get home in time to cook dinner.
Don't make a huge thing out of this. If it happened all the time then ok, you have an issue. But little things like this are normal in a relationsihp.
One thing I wondered about in your story is why did you have to go to the store to get something to cook? She found stuff in the house to cook. Did you check before you left home for the day?
Generally when I cook I plan the night before.. then in the morning I make sure things are out for thawing etc. We shop for the week parishables.. and have tons of food in the freezer and pantry. that way there are no quick runs to the store. When you are so busy those quick runs to the store can eat up a lot of time.
This is not worth messing up your home life over.. learn from it... plan ahead. Even leave her a note or tell her what you plan to cook.
And do the crock pot thing. I work a lot of long hours so I use the crock pot a few times a week. It's great.
Having said that, I still don't like that situation. Frankly, it comes across as her being controlling. He had a plan and was going to get the meal made. Is it wrong that he stopped off to pick some things up along the way? Is there a correct way to prepare meals? I don't think so, and I am leery to tell him that he needs to cook meals her way.
To the OP, are there trust issues where you aren't getting things done that you promise? Or is she controlling in that things need to be done her way.
I get your disappointment. Your wife communicates a need, you change to accomadate and meet it, and it turns out for nothing. It is reasonable to calmly address it and tell her you are upset. I don't think you need to ruin family time over it.