Exodus 24:13

And Mosheh arose and Jehoshua his minister; and Mosheh went up to the mountain on which was revealed the glory of the Shekinah of the Lord.

Moshe and Yehoshua … set out. Yehoshua accompanied Moshe as far as the foot of the mountain, where he remained until Moshe returned. That explains why Yehoshua did not know about the making of the Calf. Food would not have been a problem for him because the manna fell all around the camp.

AND MOSES ROSE UP, AND JOSHUA HIS MINISTER. “I do not know in what capacity Joshua was serving here. But it appears to me that the disciple was accompanying the master as far as the place where the limits of the mountain were marked out, for beyond them Joshua was not permitted to go, and from there Moses went up alone into the mountain of G-d, while Joshua pitched his tent there for the whole of the forty days. Thus we find that when Moses came down from the mountain it is written, And Joshua heard the noise of the people as they shouted, from which we learn that Joshua was not with them in the camp” [at the time of the making of the golden calf]. Thus far is Rashi’s language.
In my opinion, Joshua was one of the seventy elders [who were asked to ascend the mountain], for there was nobody more worthy amongst the seventy elders of Israel to approach G-d than he, and when Moses separated from them [to ascend higher], Joshua accompanied his master up to the border [beyond which he was not permitted to go]. Now do not object to my explanation on this point from what the Rabbis have said, 16. Rashi in Verse 10 here brings part of the Midrash with reference to Nadab and Abihu. concerning the punishment of these elders at Taberah, — that is, among the most distinguished and prominent ones among them, namely the elders (see Rashi ibid., Verse 1). Now the reason why the elders were singled out for punishment at that time is stated by the Rabbis as follows: Since at the time of the Giving of the Torah they gazed more intently than they were permitted to, behaving as if they were eating and drinking (see here Verse 11), they were liable to death. But since G-d did not wish to disturb the joy caused by the Giving of the Torah, He waited with their punishment till Taberah. — Now on the basis of this Midrash you might think that Joshua, too, was like the elders and unworthy of seeing Divine visions. But, concludes Ramban, this was not the case with Joshua. for they said so concerning all of them except Joshua, for he was indeed worthy to see visions of G-d and to receive prophecy.