Hi JohnB66
Yes, hogs can squeeze through surprisingly small gaps – although, it could have been a youngster. You say you are stopping putting out the mealworms at night, which is good, but hopefully the cage is also removed? A larger hog could get trapped in it. I have read about a hog having to be cut out of one, so it’s safer to remove bird feeding cages at night if there are hogs around.
Great news that you are building a feeding station and nest box for them. If you want a hog to build a nest in your nest box, it’s a good idea to make sure that there are lots of leaves (medium sized ones preferred), long grasses, etc, around in your garden. Putting a handful of material in the box can give them the idea, but most hogs like to build the actual nest themselves.
It’s also a good idea to leave a source of water available for the hogs all day every day, even during winter. You never know when a thirsty hog is going to turn up. Wide but shallow plant saucers are ideal – not so deep that a hoglet could get caught in them.
Good luck. Hope you get a tenant for your nest box soon.