From one count I have seen there are more than 300 times in the Talmud Bavli where a discussion ends with “תיקו” (let it stand, ie the question remains) yet, to my knowledge there is not a single time where this term appears as the conclusion of a discussion in the Jerusalem Talmud.
I would like to know if there is a reason that is offered to explain this phenomenon.
Rashi in Bava Metzia 85a explains why Rabbi Zeira fasted for 100 days in order to forget the Babylonian method of learning so that he could be a receptacle for the Talmud Yerushalmi with a clear mind:
דלא ניטרדיה - כשעלה לארץ ישראל ללמוד מפי ר' יוחנן ואמוראין שבארץ ישראל לא היו בני מחלוקת ונוחין זה לזה כשמן כדאמרי' בסנהדרין (דף כד.) ומיישבין את הטעמים בלא קושיות ופירוקין
When Rabbi Zeira went to Israel to learn from Rabbi Yochanan, the Amoraim in Israel weren't arguing with each other, and would work hard to come to terms with each others opinion and would answer up all reasoning without questions and answers.
We see that their method in Eretz Yisroel of learning did not involve asking questions as much, rather getting straight down to what they knew from Mesora and explaining it, without analyzing unknown cases they hadn't heard about through questioning, so there was not as many answers needed hence no Teikus.
In the Bavli, you have many times a question that was brought up in one generation, and then answered (with a source from a baraisa, for example) only generations later, such as in the times of Ravina and Rav Ashi. (There's even a rare example, in Sanhedrin 43a according to the girsa of Rabbeinu Chananel, where a question is answered by Rav Ravai of Rov, one of the Rabbanan Savorai.) Only if it wasn't resolved by then will it be labeled תיקו.
In other words, this term is part of the editorial apparatus of the Bavli. Well, the Yerushalmi didn't go through that kind of editing, so a question left open was left that way - a future generation of Amoraim, had there been one in Eretz Yisrael, could have found an answer, but there were none.
