Does a word written on a slipper that resembles the لفظ الجلالة (the majestic word for God) take the ruling of impermissibility, even if it was unintentional, and what do you advise me regarding notifying the owner of the slipper?

The aforementioned drawings do not require respect, as they are not intended to represent the name of Allah nor do they correspond to it. Mere resemblance holds no weight. Reverence is due only to the sacred things and rituals of Allah. One is advised to fear Allah and revere His sacred things, and to beware of obsessive doubts and extremism.