Yeah, that's the problem with the manga (or manhwa), it skips a lot of the details they covered. That's a different entirely it's a jade pin of the mother-consort (1st prince's mother), symbolizing her support for Yuheng. The truth of the matter is that she never lost the pin. It's apart of their plan to trick the 3rd prince into thinking she lost favor with the emperor due to the fact that she wasn't able to heal his legs and 9th and the king had fought over this. But in actuality, they were letting (spoiler alert)
The treatment was a success however it will take time for his legs to be treated but they can't reveal that yet so in hopes for the 3rd prince to not become suspicious they performed this ruse in order to protect this secret.
Okay thank you for explaining.
She was acting and wanted the 3rd prince to think she lost it he was trying to steal it anyway.
Can someone explain to me how in ch 128 she wants to return the hairpin to the emperor but in ch 209.5 the mother-consort (think that's her title) gives her the pin to wear. Did the novel explain how the pin got back to the emperor or is it a different pin. I'm just confused on that part.