There hasn't been a commercial freezer made since the 1950s that doesn't have an obvious push-lever on the inside of the door. All you have to do is lean against it to open the freezer from the inside.
It's possible for boxes to fall in the freezer, hit the door lever, and open it. You come in the next day and all your product is thawed and ruined, and your freezer motor burned out.
It is, however, possible to put a screwdriver in the security lock hole of the freezer door, which defeats the safety lever. However, kicking the door release lever will "pop out" the screwdriver or other obstruction so long as it can be removed.
It's very hard to get trapped in a freezer. That said, if the kid was an idiot, didn't know about the lever, and the lights were off, he might not see it. However, I think nearly everyone, idiot or otherwise, would simply yell his head off. You can definitely hear through the door (inside and out of the freezer).