If he did not deny it but rather claimed it was stolen or lost, he must swear the oath of the guardians. A guardian is obligated to swear three oaths: an oath that "I was not negligent with it," and a paid guardian must swear that it was not stolen and not lost; an oath that "I did not stretch forth my hand against it"; and an oath that "it is not in my possession," for perhaps it was not stolen at all. The opinion of the Rambam, of blessed memory, in the fourth chapter of Hilkhot Pikadon, and other great Rishonim, is that the primary oath that the Torah obligated a guardian is that it was stolen, and for a paid guardian that it was an unavoidable accident, and this is the oath that "it is not in my possession." The two oaths that he was not negligent and that he did not stretch forth his hand are only by way of gilgul. And that which is written, "and it be stolen from the man's house... then the master of the house shall be brought near to the judges [to swear] whether he has not stretched forth his hand," this is its explanation: "he shall be brought near to the judges" to swear that it was stolen, but this is on the condition that "he has not stretched forth his hand," for if he stretched forth his hand beforehand, he is liable even if it was stolen afterward [the Maggid Mishneh]. According to this, if there are witnesses for an unpaid guardian that it was stolen, or for a paid guardian that it was an unavoidable accident, he is exempt also from the two remaining oaths. However, there are some of our teachers who say that the oath "I was not negligent" is also from the primary oath even without gilgul; and even if there are witnesses that it was stolen, he must swear that he was not negligent, and by way of gilgul he shall swear that he did not stretch forth his hand. Therefore, if there are witnesses that he also was not negligent, he is exempt from the oath of stretching forth a hand, for we do not presume people to be wicked when there is no proof for the matter. This is the opinion of the Rosh and the Tur. And where is the oath that he was not negligent found in the Torah? For this is its explanation: "and it be stolen from the man's house" without his negligence, for if it was stolen through his negligence he is liable, and for this "he shall be brought near to the judges," which is to say that he shall swear that it was stolen without his negligence [and in the Rambam chapter 6, halakha 3, it also implies thus, though in chapter 4 it is explicit as I wrote]. And in the Yerushalmi, chapter HaMafkid [halakha 7], it also implies like this opinion. According to this, even if the pikadon is before us damaged or it died, he is not exempt from an oath, for perhaps it died or was damaged due to his negligence. And all the more so regarding a borrower, whose exemption is only if it died due to work [Netivot HaMishpat]. However, we have already explained in siman 72, section 26, that when one claims the pikadon was damaged, the Torah did not obligate an oath; see there.
לא כפר בו אלא טען נגנב או נאבד ישבע שבועת השומרים ושלשה שבועות חייב השומר לישבע שבועה שלא פשעתי בה ושומר שכר ישבע שלא נגנבה ולא נאבדה ושבועה שלא שלחתי בה יד ושבועה שאינה ברשותי דשמא לא נגנבה כלל ודעת הרמב"ם ז"ל בפ"ד מפקדון ועוד גדולי ראשונים דעיקר השבועה שחייבה התורה לשומר הוא שנגנבה ולש"ש שנאנסה וזהו השבועה שאינה ברשותי ושתי השבועות שלא פשע ושלא שלח בה יד אינו אלא ע"י גלגול ומה שכתוב וגונב מבית האיש וגו' ונקרב בעה"ב אל האלהים אם לא שלח ידו ה"פ ונקרב אל האלהים לישבע שנגנבה אך זהו בתנאי אם לא שלח בה יד אבל כששלח יד מקודם חייב אף כשנגנבה אח"כ [הה"מ] ולפ"ז אם יש עדים בש"ח שנגנבה ובש"ש שנאנסה פטור גם משבועות שתים הנשארים אבל יש מרבותינו שאומרים דשבועה שלא פשעתי היא ג"כ מעיקר השבועה אף בלא גלגול ואף שיש עדים שנגנבה ישבע שלא פשע ובגלגול ישבע שלא שלח בה יד ולכן אם יש עדים שגם לא פשע פטור משבועה דשליחות יד דאחזוקי אינשי ברשיעי לא מחזקינן כשאין ראיה לדבר וזהו דעת הרא"ש והטור והיכן היא בתורת שבועה שלא פשע דה"פ וגונב מבית האיש בלא פשיעתו דאם נגנבה בפשיעתו חייב ולזה ונקרב אל האלהים דהיינו שישבע שנגנבה בלא פשיעתו [וברמב"ם פ"ו ה"ג משמע ג"כ כן ובפ"ד מפורש כמ"ש] ובירושלמי פ' המפקיד [ה"ז] משמע ג"כ כדעה זו ולפ"ז אפילו הפקדון לפנינו מקלקל או מתה אינו נפטר משבועה דשמא מתה או נתקלקל מחמת פשיעתו וכ"ש בשואל דאין פטורו אלא במתה מחמת מלאכה [נה"מ] אמנם כבר בארנו בסי' ע"ב סעיף כ"ו דבטוען שהפקדון נתקלקל לא חייבה התורה שבועה ע"ש: