When I made my hostel reservation, I let them know that I'd be coming in at 3am via the train, and that someone should be there for when I arrive.
Well, I arrived at 4 via the bus, and when I got here, it was locked and the lights were out. There was nowhere to go so I just hung out, hoping someone would go in or come out with a key.
And yes, someone did. Some Irish guy was coming back from partying, and he let me in. Noone was there at reception, but I made myself comfortable on the large and cushy sofa until 8am when the check in desk opens.