"Was he looking at her lips?"

Translation: Díval se na její rty?

[T08Nt41c]

Because it's a one-time incident, shouldn't 'podival' be used?

[vvvpraha1]

He was looking at her lips for some time so it did not happen in one moment. Therefore you should use díval.

[knihomoll]

Díval se jí na rty?

[AgnusOinas]

Yes, that's a correct way of saying it. I've added it now.