Bava Kama 27a: If you place a vessel in the street, and someone comes and trips over it and breaks it, he is exempt from paying. Shmuel said: This rule was stated when he tripped at night.
בבא קמא כז ע”א: המניח את הכד ברה״ר, ובא אחר ונתקל בה ושברה ־ פטור… שמואל אמר: באפילה שנו.
A yeshiva bochur came to his dorm room later at night, very thirsty. Seeing a glass on the table, he filled it with water and drank it. He noticed a bitter taste, but didn’t think much of it at the time. In the morning, one of his roommates remarked with annoyance, “Where are my contact lenses?” Apparently they had been in the glass, soaking in lens solution. “I drank them,” said the bochur sheepishly. The roommate was very upset. “They cost me $200! You have to pay me for the damage,” he said.
They presented the shailah to Rav Chaim Kanievsky, who said, “You need to pay. Although it was an accident, the Gemara says אדם מועד לעולם בין בשוגג בין במזיד בין באונס בין ברצוןִ – a man is liable for any damage he causes, even if done unknowingly or accidentally (Sanhedrin 72a). Furthermore, in this case you noticed the bitter taste of the lens solution, and this should have alerted you to stop drinking before he swallowed the actual lenses.” But he advised them to ask his father-in-law, Rav Elyashiv to see if he agreed with the psak.
Rav Elyashiv did not agree, for three reasons: 1) It was not done as an act of damage, but as an act of drinking. 2) It didn’t even occur to the bochur that the cup contained contact lenses. 3) The owner of the contact lenses was at fault for placing such a valuable item in a regular glass, on a table which was meant for their common use.
Source: Divrei Siach, Bemishnasam shel Rabboseinu Rav Yosef Shalom Elyashiv and Rav Chaim Kanievsky, published on Rav Elyashiv’s first yahrtzeit, p. 34
[Rav Elyashiv considered this case similar to tripping over a pot in the street at night. Pots are not usually in the street, and he could not see it well. Here too, contacts are not usually placed in a regular glass on a table, and he could not see them.
Furthermore, Rav Elyashiv may have meant the Gemara in Bava Kama 62a, in which a man kicked someone’s chest into the river, and it turned out to have contained a pearl. If people don’t usually keep pearls in a chest, only money, then the damaging party was not expected to think of the possibility that there might be a pearl there. Similarly, even if we were to blame the bochur for drinking someone else’s water, or whatever bitter drink he had reason to think might be in the cup, we can’t blame him for the contacts, since it would not occur to him that there were contacts there.]
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