Why is Yiftach mentioning Edom's refusal to let Yisrael pass? It is not relevant to Amon!
Yiftach answered that Yisrael did not take from Amon or Mo'av. We asked to pass through, and when Mo'av refused, we went around their land. A support for this is that when Edom refused, we similarly went around their land (PF; perhaps Malbim hints to this).
How did Yisrael want to pass through Edom?
Rashi: They wanted to go from south to north, to come to Eretz Kena'an.
The Torah does not record sending Sheluchim to Melech Mo'av!
Rashi (from Tanchuma Chukas 13): Moshe hinted to this - "Ka'asher Asu Li Bnei Esav ha'Yoshvim b'Se'ir veha'Mo'avim ha'Yoshvim b'Ar" (Devarim 2:29). Just like Edom did not let Yisrael pass, also Mo'av.
QUESTIONS ON RASHI
Rashi writes that "Ka'asher Asu Li Bnei Esav" teaches that just like Edom did not let Yisrael pass, also Mo'av. "Ka'asher Asu" implies that they did [let Yisrael pass]!
Radak: Melech Edom did not let them pass through his land, which was close to Eretz Kena'an, but Bnei Esav in Se'ir let them pass (Ibn Ezra, Devarim 2:29). Similarly, Melech Mo'av did not let them pass through his land, but Mo'avim in Ar let them pass - "Atah Over ha'Yom Es Gevul Mo'av Ad Ar" (Devarim 2:18).
