I bought a greatest hits pack and it froze my game and I got back on and it was gone and I didn’t get anything
Don’t worry OP, you won’t have lost any items. What happens here is that the opening animation for the packs gets skipped over but the items do still get deposited in your REQ inventory. You need to hard reset your console to see the updated inventory in-game, alternatively you check for new items here on Waypoint: https://www.halowaypoint.com/en-us/games/halo-5-guardians/xbox-one/requisitions/categories/customization?ownedOnly=False