Question: does stefan find out about elena and damon

Answer: Yes, Bonnie stops Stefan right before he enters the burning building warning him that the fire will kill him but Stefan gets in anyway. Bonnie then stops Elena but when she sees that Elena will go in anyway, she starts chanting while holding her to prevent her from getting in. The spell calms the fire long enough for Stefan to get to Damon and help him get out. Elena and Stefan meet a little later at the Grill where Elena reassures Stefan that she loves him and not Damon, even though she cares about him.