I'm so sorry this happened to you. I stay on the 2nd floor & always lock patio sliders (4 levels including 2 in the door, chain, & the lock I bring), 3 on the room door (door lock, chain, door stopper). Much better to be safe. Cat burglers can crawl along balconies on the outside of buildings... learned that in 1987, not by being robbed but by robberies in the neighboring rooms. Always been security conscious since then. So... thefts nothing new. Usually is an unlocked door. No sense wasting time breaking in when doors are often left unsecured.