Turns out, I was wrong. Sarah decided to make up for missing the day this morning.
Yes, Sarah dressed me, a dog, in a dog mask. It makes no sense. I really should stop even trying to make sense out of what she does.
Sarah seems to have interpreted "Dress Up Your Pet Day" as "Dress Your Pet Up as a Pet Day," because I cannot fathom any other possible explanation for why she would want a dog to wear a dog mask. I guess I should be thankful that she didn't find a cat mask for me. Although it would have made more sense, it would have been that much more humiliating.