I would say there are two simple explanations for why a DIP-8 op amp like this would fail. One is it was just a faulty part to begin with. That can happen, though it would be a rarity, although if the part was purchased from eBay or the like, that's a whole different gamble (I'm not sure where this particular IC was purchased). The second reason might be that the pins saw too much heat from the soldering iron, whether that was when he was first populating the board or when he was touching up solder joints later. He's going to socket the replacement IC, so we will confidently avoid that hazard this time around.
The supply voltage was spot on, so it wasn't an over-voltage issue. Some internal component of the op amp failed and so the negative voltage rail was passing through to other pins where it shouldn't have been. That V- made its way to the positive side of C29, hence the popped cap.
Edit just because: I omitted a very obvious third possible reason, which is the IC being oriented incorrectly. That was not the case here, though.
