It looked exactly like that when I came into work on Tuesday, having not visited my office since Thursday. It was locked, in the sense that a key had been turned in the lock, but the lock wasn't lined up with the strike plate.
I know my door is stiff so I'm always sure to close it properly when I leave. Someone else with a key (so pretty well any cleaner, maintenance engineer, secretary or security officer) must have had cause to go into my office then left without shutting the door properly. This is worse than when they fixed the lights recently and did close the door but didn't lock it, because at least it didn't look unlocked.
I don't know how long my office door was left ajar, but it could have been for three whole days.
Fortunately, nothing was stolen from it. I don't know if anything was hidden in it, but there was a sniffer dog on campus today so let's hope not.