Responsa for Bava Kamma 230:5
ואם אמר לא אמר כלום והתניא מי שבא בדרך ומעות בידו ואנס כנגדו לא יאמר הרי פירות שיש לי בתוך ביתי מחוללים על מעות הללו ואם אמר דבריו קיימין
'And if he says so, his statement is of no legal validity'? Surely it was taught: If a man was walking on the road with money in his possession, and a robber confronted him, he may not say, 'The produce which I have in my house<span class="x" onmousemove="('comment',' And which was set aside as a second tithe, cf. Lev. XXVII, 30. ');"><sup>11</sup></span> shall become redeemed<span class="x" onmousemove="('comment',' In accordance with ibid. 31 and Deut. XIV, 25. ');"><sup>12</sup></span> by virtue of these coins,'<span class="x" onmousemove="('comment',' Which were about to be misappropriated by the robber. ');"><sup>13</sup></span>
Teshuvot Maharam
A. Since the books were taken by Gentile robbers, A did not lose hope of retrieving them (B. K. 114a) and thus legally retained title to his books. Therefore, B must return the books to A. B is not entitled to any compensation, since it was common knowledge that A was robbed of his books, and since B bought them from known robbers.
This Responsum is addressed to "my teacher Rabbi Eliakim."
SOURCES: Pr. 1009; Cr. 196–7; Mord. B. K. 163.