I’m upset with my aunt for swapping my piece of cake with hers behind my back?

So recently I went shopping with my mom and aunt. We went to a market and got 2 slices of cake- which I paid for, 1 for her and 1 for me, and each slice was placed in a separate bag. I got the slice that had less crust on the outside as it was my preference. There was one final shop that my mom and I went into whilst my aunt waited outside. I left my slice of cake that I was holding with her, and at the time I remember feeling an inkling that she would swap it whilst I was in the shop. At this time her slice was inside another bag of hers so it was out of view. So later, when I got out the shop, I looked inside the bag. The slice had changed. She must have looked inside the bag, preferred my slice and changed it without saying anything. I really don’t know how she could have mixed them up as her slice was in its bag inside her bag. I wouldn’t have minded if she had just been honest and told me which slice she preferred, and I don’t care about the cake, it’s just the going behind my back that upset me. Should I mention it or leave it?
I’m upset with my aunt for swapping my piece of cake with hers behind my back?
Post Opinion