Is expiation required for one who swore by Allah regarding the validity of a phone number, and then it was discovered to be wrong, despite his claim that it was a 'laghw al-hadith' (unintentional or vain oath)?

Scholars have differed concerning the "Laghw" (idle/vain) oath: The Hanafis and Malikis hold that it is an oath sworn based on one's assumption which then turns out to be contrary, unless it pertains to the future according to the Hanafis, or to the present or future according to the Malikis, in which case it is not considered Laghw and requires expiation. The Shafi'is hold that it is what slips from a speaker's tongue without intention. The Hanbalis hold that it is of two types: an oath sworn concerning something one believes to be true as sworn, but which turns out to be otherwise; and what slips from a speaker's tongue without intention. The latter is the most preponderant view, based on Allah's saying: (Allah will not impose blame upon you for what is unintentional in your oaths, but He will impose blame upon you for what your hearts have earned). So, if the one swearing an oath believes what he is swearing about is true, but reality contradicts his assumption, there is no expiation or sin upon him, because it is a Laghw oath. However, if he swears falsely, it is a "Yamin Ghamus" (a false oath taken knowingly), which has no expiation, and he must offer sincere repentance and increase in righteous deeds.