It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that a woman or a man used to look after the mosque. He (peace and blessings be upon him) missed that person and asked about them. They said: That person has died. He (peace and blessings be upon him) said: "Why did you not inform me? Show me the grave." They showed him (peace and blessings be upon him) the grave, and he (peace and blessings be upon him) offered the funeral prayer over it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 7012