Understanding this incomplete sentence

Question

I'm not quite sure how to understand the second sentence below as it looks incomplete to me. If it was because the speaker interrupted what he was saying with the next line then I would have expected something to indicate this. Could someone help me understand which of the following this is:

• There something implied after the は
• It is incomplete because the speaker interrupted what he was saying.
• Something else I haven't thought of

「ねえ、このあとメロンパンを買いに行くの。一緒に行かない？」

「メロンパンかあ、確かに甘いものは」

「あ、悪い。このあと引っ越しの片付けなんだ。荷物をほどかないと」

Answer 1

That sentence in question has nothing to do with common "incomplete-looking" constructions like "行かないと" ("I must go") or "見ても?" ("Mind if I take a look?").

From what I can see, it can be a "true" incomplete sentence. Simply, there are three people in the scene, and the third speaker interrupted the second speaker while he was still speaking. Or else, if there are only two people, it means the second speaker suddenly remembered why he cannot go with her while he was still speaking. Anyway, if this is from a novel or a manga, there is almost certainly some hint regarding what happened.