Moses's promise is exact and generous. Targum Pseudo-Jonathan on Exodus 8:7: The frogs shall depart from thee, and from thy house, and from thy servants, and from thy people; and those only that are in the river shall remain.
Read the geography. Palace — cleared. House — cleared. Servants — cleared. The people — cleared. The riverbank is the border. Frogs belong in water; they will go back to being ordinary frogs in an ordinary river. The plague will retire without a trace of itself except in its natural habitat.
This is a quiet lesson about how God ends punishments. The miracle does not vaporize the frogs — that would have been easier. God sends them home. What was out of place returns to where it belongs. The world is restored, not replaced.
There is something hopeful here for a suffering listener. When Jewish history turns, when the exile finally ends, the upheaval does not mean the old world is destroyed. It means things return to where they belong. Israel to the land. Torah to public life. The tyrant's plagues to their source. Everything else — ordinary rivers, ordinary frogs, ordinary mornings — resumes.
The takeaway: God's redemptions are less about erasure than about restoration. The frogs stay in the Nile where they always should have been; only the invasion ends.