I'd say, maybe mister is not a very good driver. If he did notice running over something, he should stop and check. No one knows if it IS just a yukkuri or not.... especially in a park.
1) Driver being savvy enough that he knows 99% of the time he may run over a yu since they are the most prone to get run over of all the creatures in the yu world and it's nearly a fact in the yu world, yukkuri crossing roads have huge probabilities of being run over.
2) maybe the untranslated scream is a YUGYAAAAAAAA! aka "well it was a yukkuri, no biggie".
Maybe just a trash or dead branch. Crushing a soft yukkuri wouldn't be really noticable, and he could mistake little Marisa's screaming with daddy Marisa's. I think what he felt is the Suii, not Marisa.