Does it constitute a definitive oath to sever the relationship if the suitor swore to end the engagement should his fiancée leave and he then followed her but could not find her later?

The fiancée is a stranger to her fiancé, so it is not permissible for him to go out and sit with her without a mahram. The Sacred Law has permitted him to look at her and speak with her without lust, solely for the purpose of getting to know her. Each of them remains a stranger to the other until the marriage contract is concluded. Regarding the occurrence of a sworn-upon matter unintentionally, the preponderant opinion is that no breach of oath occurs, and no expiation is required.