what do you do ?
Talk to supervisor. If no supervisor, depends on how bad you need the job. Stay and cover, then report to supervisor in morning if you need to keep the position. Just leave if you don’t.
For the purpose of your job application just put wait a while and if nobody shows up inform your immediate superior and let him take a decision. If he requests you to continue working, request the right to be paid overtime for it. In the actual job I’ve seen many employees simply check out not caring if the next person has shown up yet. At the hospital I used to work the night shift doctors would show up 1 hour after the previous doctor’s shift was up. This was due to a manger’s decision to have a faulty schedule leaving the service empty for 1 hour every week. It would be silly to force the afternoon shift doctor to work 1 hour extra everytime if this has nothing to do with him or the night shift doctor. We’d simply close the service informing everyone to be patient and wait 1 hour or go to a nearby hospital instead. In some services managers were expected to cover shifts for their inferiors that didn’t show up.