Q. How did Rav Shimon bar Yochai and his son comply with the mitzva of suka while they were in the cave?
A. On question 2197 regarding the opinion of the Chasam Sofer that the mon began to fall on Lag Baomer, we wrote: "Sifsei Tzadik (Lag Baomer 5), questions how Rasb’i and his son were able to comply with all the mitzvos such as kiddush, chalos, matza, maror etc. during all the years they spent eating the choruv tree fruits inside the cave. He explains that the fruits possessed the qualities of the mon that rained on the Bnei Yisroel while they were in the desert. (See Shaar Reuben p. 545 quoting similar from Zohar), and they complied with mitzvos in a similar way."
However. Talmud (Shabbos 11a) debates whether Rashb"i normally would even stop his learning for davening, see Tosafos there. Nevertheless, Yerushalmi (Brochos 1: 2) maintains that Rashb'i would stop Torah learning, even for making a suka.
Shaarei Hamoadim (p. 393) is of the opinion that the years Rashb"i and his son where at the cave, they were inhabiting the "Almo D'eischasio" or the hidden world, and he didn't have to comply with physical mitzvos (maasiyos).
Horav Shlomo Miller's opinion is that he would have been exempt anyway from seating in a suka, as other travelers are while on their way. (Suka 25a, Shulchan Aruch O.H. 640: 8)
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit'a
Important Numbers
