The original sentence has no problem. What may confuse you is that "ser" and "ir" both have the same conjugation in the past: fui, fuiste, fue, etc. With some practice you will get used to it: Tu siempre fuiste a estudiar a casa de tus amigos y fuiste un excelente estudiante. (ir y ser)

Utiliza el verbo "ir"

'Tú fuiste a la universidad ayer' would literally mean 'You went to university yesterday', so you're right in assuming the verb 'estar' should be used when referring to someone who is at a specific location, as in your example, 'You were at the university yesterday' meaning 'Tú estuviste en la universidad ayer'. However, I'd like to point out that this verb is often used to refer to a state such as being ill, as in 'Estuviste enfermo ayer'. Notice that I didn't add 'Tú' in my example. I suppose your tutor added the pronoun 'Tú' just to provide you with a more direct translation, but keep in mind that we tend to omit pronouns in Spanish unless we intend to add more emphasis for some reason. Finally, I agree that your tutor must have made a mistake or got distracted. I guess it happens to all of us from time to time. :)

Hello Steve, maybe in class the teacher gave you these examples to compare and distinguish the meaning of the two sentences: 1. Tú FUISTE A la Universidad ayer = You WENT TO the university yesterday and 2. Tú ESTUVISTE EN la universidad ayer = You WERE AT the university yesterday because many students confuse them. Well, I think the important thing is that you can use this difference between FUISTE A and ESTUVISTE EN in any reference to a place: 1. Fui a Roma el año pasado 2. Estuve en Roma cinco días.