From Sahih Muslim (Hadith 4503):
Zaid b. Khalid al-Juhani reported:A person asked Allah's Apostle (ﷺ) about a lost camel; Rabi'a made this addition: He (the Holy Prophet) was so much annoyed that his cheeks became red." The rest of the hadith is the same. He (the narrator) made this addition:" If its (that of the article) owner comes and he recognises the bag (which contained it) and its number, and the strap. then give that to them, but if not, then it is for you
Reference: Muslim 4503