In explaining why H’ told Yitzchak not to go to Mitzrayim, the Medrash (Bereishis Rabbah 64:3) says:
?”? ?????? ?? ???? ????? ?? ???? ?? ???? ??? ?????? ??? ????? ?? ?? ?? ???? ??? ???? ?????
Rashi (26:2) explains that Yitzchak thought to copy Avraham and go to Mitzrayim and therefore H’ had to tell him that he can’t go because he was an ???? ?????.
Rashi earlier (25:26), writes:
????? ?? ??? ???? ??? ?????? ??? ?????? ????? ???? ?????
which would indicate that Yitzchak knew that he was an ???? ????? before H’ told him not to go to Mitzrayim, in which case he should have known on his own not to go. It seems unlikely that Yitzchak knew that he was an ???? ????? and that therefore he shouldn’t marry a shifcha yet he didn’t know that ???? ?? ???? ??? ?????? ??? ?????.