Whatever that might be, he could well have done that. Let me tell you during a move, one of the things you do not want to do is lock yourself out of your new house.
I certainly isn't fun.
When we bought our first house last year we got the call to the EAs office to collect the keys. After waiting there for 30 minutes they admitted they couldn't find them and had to call a locksmith.
The locksmith couldn't come until 9pm and changed the front door lock for us, it turned out the keys were on the kitchen counter and the EA had just left them there and walked out the door. Twits.