Sounds like Cell

Stevethebarbarian was saying: I think all of you are reading too deep into the mood shift. Gohan is just a little bummed to have to answer that question, since he has to tell Trunks “welllll… your father’s pretty much functionally also dead, is beyond revival, and has been for 20 years. Goku actually did come back, but now he’s gone too.” It’s not like Vegetto’s existence is a tragedy or anything, but Trunks is obviously looking forward to hearing about his father, and it sucks to let him down.

(Also I’m just realizing telling the whole story also includes “your dad went evil and murdered a bunch of civilians before he permanently stopped existing btw” which is also a bummer.)
People are "reading too deep" because Gohan's reaction is too intense for what you described. If that's what the artist is going for, they overexaggerated the expression. Gohan doesn't look a little bummed, he looks angry.