To where did Yehoshua tell them to come?
Rashi (from Bereishis Rabah 5:7): They were all between the staves of the Aron. 1 This is one of the places in which a small [place] housed a large amount. 2
Radak: It was in front of the Aron, where Yehoshua was.
Radak (10): This Drashah is difficult. If such a wonder was done, the Navi would have recorded it! (Many Midrashim teach about great miracles not explicit in Tanach. Hashem folded up all of Eretz Yisrael under Yakov, when he slept (Chulin 91b). All Bnei Yisrael were healed before Matan Torah (Bamidbar Rabah 7:1), died and were revived twice, and afterwards every wife became pregnant with a male. Hashem stopped the sun for Moshe, like for Yehoshua (Ta'anis 20a)
