Imam al-Shafi'i (may Allah have mercy on him) said: "Then outwardly it (the item) is divided between the two of them in halves; and if neither of them finds proof (testimony), we will make each of them swear an oath against the claim of the other."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الدعوى والبينات / Q21213