Mix up and not sure how

I went to the post office yesterday and printed out labels. I had 7 packages that I needed to ship out. While I was there I noticed someone purchased an item so I printed the label that way when I got home I can just throw it on the package. Well, today I woke up and it says THAT package was sent. So I obviously messed up somewhere. The 7 packages I was there for originally were sent. How could I possibly of messed this up?! I still have the label of the package that shows shipped in my car. Did I mix up 2 packages or 1?