「バッグをぎゅっと抱きしめる」は英語で次のように言えます。
ーto hold one's bag tightly against one's chest
例:
A boy became separated from his friends in the mountains and started crying walking along all by himself, so he squeezed his favourite bag tightly against his chest.
「少年は山の中で友達から離れ離れになり、泣きながら一人ぼっちで歩いていたので、その少年は彼のお気に入りのバッグを胸にぎゅっと抱きしめた」
to become separated from ... で「…から離れ離れになる」
to squeeze one's bag tightly against one's chest ということもできます。
ご参考まで!