Reference for Bava Metzia 55:18

אמר ליה אביי והא כתיב (נחמיה ז, עב) וישבו הכהנים והלוים וגו' (עזרא ב, ע) והמשוררים והשוערים וכל ישראל בעריהם

<b><i>GEMARA</i></b>. A Tanna taught: The neighbours of the loss [are referred to in the Mishnah]. What is the meaning of 'the neighbours of the loss?' Shall we say, the neighbours of the loser? But if they know him [who lost it], let them go and return it to him! — But [it means] the neighbours of the vicinity wherein the lost article was found.<span class="x" onmousemove="('comment',' And R. Meir's reason is that it is probably theirs. ');">¹⁶</span>

Jastrow