Rashi on Genesis 42:27/רש"י על בראשית מ״ב:כ״ז

1ויפתח האחד literally, AND THE ONE OPENED HIS SACK — This was Levi who remained alone (one) being without Simeon his companion (cf Targum Jonathan).

2במלון means the place where they stayed over night — THE INN.

3אמתחתו is the sack (שק) just mentioned.