The Big Blunder and the Big Miscalculation (大失態と大誤算) is the eighteenth chapter of the DanMachi manga.
At the Guild, Bell was discussing with Eina about Lili. Eina didn't have any problems with Bell having a supporter until she heard that Lili was from the Soma Familia. She warned him about adventurers from the Soma Familia. He took her advice to heart and asked something else on his mind, which was the treatment of supporters. Eina explained to him that adventurers often looked down on supporters because of their work. Bell expressed his disgust at their poor treatment and thanked her for the information. As Bell turned to leave, Eina noticed that his Hestia Knife was missing and pointed it out to him. Not sure of what she meant, Bell told her that his knife was there, only to realize that it was missing. Both Bell and Eina realized the terrible situation that they were in.
In another part of Orario, Lili visited Bom Cornwall's shop. Lili handed the Hestia Knife over to have him take a look. Bom looked over the knife and told her that it was junk. She angrily took the knife and left the store.
Lili couldn't believe that the Hestia Knife was worth so little, not knowing that the knife's true power could only be used by members of the Hestia Familia. She knew that she could get a much better price if she had the sheath with the Hephaestus logo. She quickly hide the knife when encountered Syr and Ryuu in the alley. However, Lili wasn't able to hide it fast enough as Ryuu demanded for Lili to show her the knife. Lili claimed that the knife was hers. Unfortunately for her, the only knife with hieroglyphs that Ryuu knew was Bell's knife. She tried to run but was hit by an apple thrown by Ryuu, forcing her to drop the knife. Ryuu followed up with a kick that sent her flying.