This is what is mentioned in the SGI Library:
parable of the jewel in the robe [衣裏珠の譬] (Jpn eriju-no-tatoe )Also, parable of the gem in the robe or parable of the jewel sewn in the poor man's robe. One of the seven parables in the Lotus Sutra. It is related in the "Five Hundred Disciples" (eighth) chapter by five hundred arhats to demonstrate their understanding of the one vehicle teaching. It tells of an impoverished man who goes to visit a close wealthy friend. Being treated to wine, he becomes drunk and falls asleep. The wealthy friend must go out on business, but before leaving, he sews a priceless jewel into the lining of his sleeping friend's robe. When the poor man awakens, he has no idea that he has been given the jewel. He then sets out on a journey. To provide himself with food and clothing, he searches with all his energy, encountering great hardship. Being always in want, he is content with whatever little he can obtain. Later he happens to meet his old friend, who is shocked at his poverty and shows him the jewel in the robe. The man realizes for the first time that he possesses a priceless jewel and is overjoyed. The five hundred arhats explain that, just as this man was ignorant of the treasure he possessed, so the Buddha's disciples were unaware that the Buddha had caused them to plant the seeds of an unsurpassed aspiration and were instead satisfied with provisional teachings and a small portion of nirvana.[quoted from here]