וְהָיָ֞ה אֲנִ֣י ׀ אֵלֵ֣ךְ מֵאִתָּ֗ךְ וְר֨וּחַ יְהוָ֤ה ׀ יִֽשָּׂאֲךָ֙ עַ֚ל אֲשֶׁ֣ר לֹֽא־אֵדָ֔ע וּבָ֨אתִי לְהַגִּ֧יד לְאַחְאָ֛ב וְלֹ֥א יִֽמְצָאֲךָ֖ וַהֲרָגָ֑נִי וְעַבְדְּךָ֛ יָרֵ֥א אֶת־יְהוָ֖ה מִנְּעֻרָֽי׃
And it will come to pass, as soon as I am gone from thee, that the spirit of the LORD will carry thee whither I know not; and so when I come and tell Ahab, and he cannot find thee, he will slay me; but I thy servant fear the LORD from my youth.
From David to Destruction
Radak and Ralbag solve the problem by noting that Eliyahu HaNavi would only appear erratically. He would most often seclude himself in Chassidic style “Hitbodedut” to focus on his spirituality. The Bnei HaNevi’im believe that Eliyahu HaNavi has departed only temporarily, as has happened in the past, and that a search will successfully locate him. Indeed, the righteous Ovadiah in Melachim I 18:12 comments that Eliyahu HaNavi’s precise location can never be determined, since “the spirit of Hashem could spirit [him] off to the unknown” at any time.
Rashi
That they did not find you. For the nation was unable to find you.2Below v. 12.