I think you may be thinking of Osteria de Poeti
There are no end of "hidden gems" in Bologna, the entire town almost qualifying for that, but in my mind, the most important and rewarding things to see that are unique to Bologna are:
The anatomical theater in the Archigennasio -- you reach this by walking down the left side of the San Petronio as you face it).
The terracotta sculpture group in the church of Santa Maria della Vita, only open in the mornings, in the via Claveture
The oratorio of St. Cecilia on the via Zamboni 15 (and take in the old Jewish ghetto while you are there)
The choir stalls behind the altar in the church of San Domenico
The Medieval museum (skip the first few rooms)
The Papal Legate rooms in the Palazzo Communale
The art museum of Bologna also has an excellent collection and might as well be on the moon for all the people who go.
If you like coffee, the Caffe Terzi, in the via Oberdan, makes the very best in Bologna. If you likes sweets and a scene, the cafe Zanarini is a swank spot in the piazza Galvani. For cocktails, track down Le Stanze in the Borgo San Pietro (but hang on to your receipt when you pay. It will be checked at the door when you leave.)
One shouldn't leave Bologna without sampling excellent stuffid pasta. My recommendation would be trattoria Anna Maria in the via delle Belli Arte for their filled pastas in gorgonzola sauce or in broth.
Edited: 1:33 pm, May 23, 2012