Indra was not left the place still, when the sage returned. Indra and Ahalya were both cursed by the sage. Indra had to lose his testicles and his body was tainted with a thousand marks of vulva on his body. Ahalya was to be turned into a stone. On her entreaties, the sage took pity on her and declared that she would take her original form, the moment Sri Rama touched her in Treta Yuga. It is said in the Ramayana, that Sri Rama, while wandering in the forests of Dandaka, touched Ahalya with his feet and restored her to her former state.
References :
1. Kohli, Surindar Singh, Dictionary of Mythological References in Guru Granth Sahib, 1993