My research did not confirm the details I will cite here, but I will share with you the reason the silver coin was so important to the woman who lit the lamp and swept the corner of the room til she found the coin. The coin was an embellishment on a headdress she had worn on her wedding day. There were ten of the coins and they were a part of her dowry. She had kept them safe and worn the ornament only on very rare and festive occasions since she married.
Losing even one of the coins was a serious loss for her. It represented so much of her family pride and symbolized the joy she shared with her husband. She shared with her friends the crushing sadness of the loss, so the joy of recovering it was great indeed.
She called all the neighbors and friends and showed them her prized possession. It was a day to wear her finest dress even if it wasn't a holiday and even if there was no procession. Her joy knew no bounds.
So it is in heaven when a lost soul is recovered: The angels in heaven rejoice!