When Indra saw the thunderbolt return from the enemy, he was very much afraid. He began to wonder whether this had happened because of some miraculous superior power

Expressions researched:
"When Indra saw the thunderbolt return from the enemy, he was very much afraid. He began to wonder whether this had happened because of some miraculous superior power"

Srimad-Bhagavatam

SB Canto 8

When Indra saw the thunderbolt return from the enemy, he was very much afraid. He began to wonder whether this had happened because of some miraculous superior power.

SB 8.11.33, Translation and Purport

When Indra saw the thunderbolt return from the enemy, he was very much afraid. He began to wonder whether this had happened because of some miraculous superior power.

Indra's thunderbolt is invincible, and therefore when Indra saw that it had returned without doing any injury to Namuci, he was certainly very much afraid.