We learnt about the 3 people who spoke incorrectly in Taanis 4.
1) How come it didn't include Yisro. He said "Whoever can pull out this stick can marry my daghter. That also could be a blind or lame woman. How come it doesn't count that?
2) Also why didn't Yiftach Hagiladi get a proper response while Eliezer and Shaul got a good response?
1) Two possible answers to your first question: a) This episode is not mentioned in the Torah, the others are. Proof of this lies in the fact that the Gemara cites a Pasuk for each of the three cases. b) Because Yisro was a gentile at that time, and the Gemara is concerned with the mistakes made by leaders of Klal Yisrael, not those of gentile idolaters.
2) Your second question bothers the Iyun Ya'akov too. He explains that whereas Eliezer and Shaul needed to initiate a Siman, each for his own needs of the moment, and each for a Devar Mitzvah, Yiftach had no need to make such a stipulation. If he wanted to bring a Korban, then he ought to have said that he would bring the best sheep. Also, Eliezer figured that if the girl was such a Ba'alas Chesed, then she would probably be worthy of Yitzchak in other regards too (perhaps he also relied on the merit of Avraham and Yitzchak); while Sha'ul figured that whoever would kill Goliyas and save Klal Yisrael, would most likely be someone who was worthy of marrying his daughter. Yiftach on the other hand, did not have such merits to rely on.
Be'Virchas Kol Tuv
Eliezer Chrysler