Umar sought the help of the descendants of the Prophet, invoked Allah through them, and his wishes were fulfilled. I refer to only two such occasions.
Ibn Hajar Makki writes in his Sawa'iq-e-Muhriqa, after verse 14 (from The History of Damascus) that in the 17th year of the Hijra people prayed for rain but to no effect. Caliph Umar said that he would pray for rain the next day through the means of approach to Allah. Next morning he went to Abbas, the uncle of the Prophet and said: "Come out so that we may invoke Allah through you for rain."
Abbas asked Umar to sit for some time so that the means of approach to Allah could be provided. The Bani Hashim (Ahle Bait) were then informed. Abbas then came out with Ali, Imam Hasan, and Imam Husain. Other Bani Hashim were behind them. Abbas asked Umar that no one else be added to their group. Then they went to the place of prayers where Abbas raised his hands for prayers and said: "O Allah, you created us, and you know about our actions. O Allah, as you were kind to us in the beginning, so be kind to us in the end." Jabir says that their prayers had not ended when clouds appeared and it began to rain. Before they could reach their homes, they were drenched. Bukhari also reports that once during the time of famine Umar Bin Khattab invoked Allah through Abbas Bin Abdu'l-Muttalib and said: "We betake ourselves to our Prophet's uncle with you; so Allah, send down rain." Then it began to rain. Ibn Abi'l-Hadid Mu'tazali in his Sharh Nahfu'l-Balagha (Egyptian edition), page 256, writes that Caliph Umar went along with Abbas, the uncle of the Prophet, to invoke Allah for rain. In his prayers for rain, Caliph Umar said: "O Allah, we betake ourselves to your Prophet's uncle and of his ancestors and of their remaining respectable men. So guard the position of your Prophet through his uncle. We were guided toward You through the Prophet so that we may seek their help and do repentance."
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I am not sure if I could not read your answer properly or you did not read my question.
Bhai, I was asking an example of a sahabi saying "Ya RasoolAllah" not "Ya Allah"