So, Brandon. Hoid. I remember you saying at the Idaho Falls signing last year that he was in Well of Ascension. We, your dedicated fans who like scouring books searching for obscure characters who have any possibility of being the mysterious Hoid, have yet to find him. Peter sent us on a hunt for him (Hoid, not Peter...) in the deleted scenes, and we found his boot-print.
Now, I think he broke the pottery there too—the one holding the lerasium—and since there's broken pottery in the actual version, I think he may have snuck into the cavern and broken it as well. If so, is this Hoid's part in Well of Ascension? This trace of him? I commend you if it is. It is clever, making us think it was a person, when in fact it's just something he did.
You are on the right track, but wrong on one point. Hoid does appear in the book.
I had originally toyed with making his touch on the novel more obscure, but decided that I wanted to be consistent with the other novels by actually having him appear. Once I realized I'd probably cut the scene with the footprint, I decided I needed this actual appearance even more badly.
Fortunately, I knew what Hoid had been up to all this time, and had placed him in a position where several characters could run into him. In Well of Ascension, Hoid believed (as Vin did) that the Well was in the North, even though it was not. He spent much of the book pursuing this idea.
Through events, however, he discovered he was wrong. He made the realization after Vin did, but only because of a chance meeting. (This is recorded in the books. Let's just say he was listening in when someone implied that the Well was in Luthadel.)
He hurried to Luthadel, and was in the town, skulking about in the last parts of the novel. He isn't seen here, though he does still infiltrate the Well. (Hoid is quite proficient at manipulating Shadesmar for his own ends.)