Radak: This was a Hora'as Sha'ah. The angel said "v'Im Ta'aseh Olah la'Shem Ta'alenah" (verse 16).

R. Shimon (Zevachim 119a): "Ki Lo Vasem? El ha'Menuchah v'El ha'Nachalah" - both of these refer to Yerushalayim. There was no Isur Bamos when the Mishkan was in Shilo. (This is unlike the Stam (majority) opinion. - PF)

Radak: The angel did wonders to make fire come from the rock ¹ and consume the kid and the Minchah, and when the flame rose, the angel rose, i.e. it vanished from their eyes, in the flame.