I'm not sure what number the rule is, but this happens to me a lot:
Within days of sending someone a package, you will come across another card that you wish you'd included in the package.
Case in point (although it is a sticker)
And of course, I'm quite likely to misplace this between now and the next mailing. Because I'm an idiot.
And since a 4 card pack isn't really enough for a single post, I'll tack it onto this one. Now I can go back to ignoring this product in both the retail and hobby environment. But I might hunt for singles of Senators, especially Karlsson, since he's in the white alternate jersey.
And the fourth card, which should be either a hit or a numbered card.