So it was an absconding then, not a swarm. 
I haven’t, but lots of people have.
Your photo shows you harvesting from the front of the hive. Unless you re-tilted the hive, that means that your hive was tilted backwards, which is the wrong way round and can cause leaks. Your tube is also very full of honey. That can cause airlocks and force honey back into the hive. To avoid this, open the frame in 25% sections, waiting 10 to 20 mins before advancing the key to the next section. If you always make sure that there is air in the top of the Flow tube, you can minimize leaks. Here is a video of what I mean:
