Teflon in general
The Teflon coating is not clear halachicly if it can be kosherd as it is compared to somewhat of a plastic, which we are unsure what its halachic status is regarding to koshering is it like cheres- earthenware which one cannot kosher, or like metal which can be koshered, therefore some poskim are machmir not to kosher it all year round. while others are machmir specifically with regards to pesach where we are extra machmir as chametz is forbidden even b’mashu (even a drop). while other more lenient kashrus agencies allow one to kosher it for pesach as well.
kosher a frying pan
If non-kosher food was fried in oil in a frying pan, one can kosher the pan by heating it to the point that paper will become singed when in contact with the other side of the heated metal. If it was used without oil, it is not feasible to kosher it since it must be heated until it glows red-hot which almost always will ruin the pan.
The rule is that we do not Kosher Teflon-coated utensils for Pesach because they are designed for use even without liquids such as oil, therefore their koshering is with Libun Chamur, but because Teflon utensils get ruined by Libun Chamur we fear he will spare them and not do Libun well. Nevertheless, in this case because it was used only once, if it is known that it was used with liquids, it can be koshered by Hagalah. According to the opinions which allow one to kosher Teflon.
In practice, one cannot kosher a Teflon frying pan for pesach and with regards to Teflon in general if its not a great loss one should be machmir.
Additional point.
If one fried a regular egg which had a blood drop on it in a Teflon pan contemporary poskim allow one to kosher it with hagolo after 24 hours.
