Commentary for Bava Metzia 42:7

ת"ש מעות מפוזרות הרי אלו שלו אמאי הא לא ידע דנפל מיניה התם נמי כדרבי יצחק דאמר אדם עשוי למשמש בכיסו בכל שעה ושעה הכא נמי אדם עשוי למשמש בכיסו בכל שעה ושעה

Come and hear: SCATTERED MONEY, [etc.] BELONG TO THE FINDER. Why? [Is it not a case where the loser] did not know that he lost it? — There also it is even as R. Isaac said: A man usually feels for his purse at frequent intervals.<span class="x" onmousemove="('comment',' B.K. 118b. So that he is bound to miss the money very shortly after he has lost it. ');">¹²</span> So here, too, [we say,] 'A man usually feels for his purse at frequent intervals' [and soon discovers his loss].

Rashi on Bava Metzia