I'm a little confused about this situation, can they do that?

Ok so I'm 15, while my mom works I stay in the apartment with my 5 year old sister. The BIGGEST rule is NEVER open the door for anyone but her. It's summer so I stay up all night and sleep until like 2 or 3. I was asleep with my little sister in the bedroom (it was about 2 pm) and I woke up when I heard banging on the door. I decided to check my phone to see the time, and realized my mom couldn't possibly be off work. I was groggy and tired so I decided to go back to sleep since I figured they would go away. Next thing I hear is the door being busted open. We have the normal lock that they have access to, and a second lock that we use when I'm home alone or with my sister. They pushed on the door so hard that the door broke open, then they walked in and checked a vent for about a minute. I was up by then and, since I was half asleep, I was trying to make sense of the situation. After hearing the man say "I can't figure this out" and leaving, I started wondering if they can do that. I know they can have maintenance checks when we aren't home, but if the door is locked can they still come in? I know if it's about the time when people are awake that they might have been able to do that. I'm just a little confused here.