An egg roasted by an idolater - Bar Kapara permits it and Chizkiyah prohibits it.

Question: This discussion applies when the idolater intended to roast it, but if he did it accidently, what is the law?

Answer: There was once a fire ignited by an idolater in order to clear out an area in which canes were growing and an area in which date palms were growing. There were grasshoppers there and they were roasted in the fire. The question came before R. Mana (as to whether the roasted grasshoppers were prohibited because they were 'roasted by an idolater'). R. Mana prohibited them.

Rejection (R. Abahu): The reason he prohibited them was because non-Kasher grasshoppers were part of the mixture.

(R. Yosi bei R. Bun): (Having learned earlier that Rav was stringent with their oil, the Gemara now cites) further examples of Rav's ruling stringently, (as cited in Yerushalmi Shekalim). Rav went to Bavel and saw that they were lenient with meat that was left in the hands of an idolater and he was stringent with them to prohibit it (if it left the sight of a Jew)...

A person was once walking in the marketplace carrying meat. A Daya (type of stork) came and snatched the meat from him. When the bird flew away, a piece of meat fell to the ground. The person wanted to take back the meat, but Rav told him that it was prohibited to him, as there was a concern that the bird had been carrying Neveilah meat that fell instead of the Kasher meat.

A person once went to rinse a piece of meat in the river. He forgot the meat next to the river and when he remembered it, he wanted to go back and take it. Rav told him that it was prohibited, as (we could say that perhaps) the river washed away the Kasher piece of meat and another (non-Kasher) piece washed up over there.