No, I think the invisible thing only affects stuff when Carbuncle's directly involved. I used to draw him when I was a kid, and people could see those just fine. Actually, I have a figurine now-

[He fishes around in his pocket, emerging a moment later with a little carved figure of Carbuncle, in a similar style and material as the carving Pyra herself would have received from Era earlier in the month.]

I can still draw it if you want, but for right now, this is what it looks like.