Is what happened considered a sin, and what is the solution for this intrusive thought?

Islamic law commands both men and women to lower their gaze, as Allah Almighty says: "Tell the believing men to lower their gaze," and "And tell the believing women to lower their gaze." Moderation should be observed in lowering the gaze; one should lower their gaze from what is forbidden without excessive strictness. If a person looks at something permissible, they should not succumb to the whispers of Satan. There is no sin upon the questioner for what was mentioned, and the solution is to turn away from whispers that are not based on rational or textual evidence.