I don’t think teams allow other teams in their garages. They don’t want them to see setup etc...
They don't have separate garages, they have bays. And everybody pretty much knows each others' "set up". If it happened after the rain postponement, the cars and equipment are stowed, everyone is kicked out and the garage is locked up until the morning. They called the postponement a little after 5pm so things were probably locked up by 8:00...ish?