Yosef Karo

“ However something that cannot be permitted by a person, and will not certainly become permitted in the future, is not considered a devar sheyesh lo matirin. Therefore an egg, about which we have a doubt whether or not it is born of a treifah animal, that becomes mixed up with other eggs is not considered a devar sheyesh lo matirin since it will not certainly become permitted in the future and there is nothing a person can do to permit it. ”