פירוש על קידושין 65:10

The Talmud resolves the difficulty—in the inner rooms, one need not rise in front of a sage. But in the outer rooms, he must.
The idea that Bar Kapara was in an outer room is also logical, for if he were in the inner room, he would not have been allowed to even think about Torah.
However, this last support for the resolution is not certain. It is possible that Bar Kapara was in the inner chamber and was thinking about Torah, even though he should not have been doing so. After all, one does not always have control of one’s thoughts.