I always thought that だ is only used after a noun or an adjective...but the だ appeared right after the verb 見た in the sentence above, which really confuse me.
Think of だなんて as a single colloquial unit instead of associating the だ with the preceding bit. In fact, considering everything prior to that in quotations or brackets may help.
といったらありはしない is usually, or rather, ALWAYS used as the contraction form ったらありゃしない.
Google search result
といったらありはしない 約 15,400 件
ったらありゃしない 約 4,460,000 件
As you can see the seach result for "といったらありはしない", MOST OF ALL of them are explanations or example sentences of this structure especially for non-native learners or JLPT. I have never heard or seen the original/non-contracted form actually used.