Welcome to the Forum!
I’m surprised there are still sites saying mealworms are o.k. for hedgehogs! They are a definite no. They have an imbalance of phosphorous and calcium which can cause calcium to be leached from the bones. They are particularly dangerous for hoglets who can grow in a deformed way. Unfortunately hogs love mealworms and sometimes can become addicted to them and not want to eat anything else. As you can imagine this can cause problems for people trying to treat these hogs if they refuse to eat decent food.
Some people may claim that it’s o.k. to feed mealworms in small amounts. The problem with that is, because they love them, they may seek them out and if others also fed them, they could potentially end up with a diet predominantly of mealworms, even though one individual may only be offering small amounts. Hogs will also visit bird tables for any food spilt, so may also pick them up from there. So it’s best that anyone who is providing supplementary food for hogs provides the best they can, so cat/dog/hog food or cat/kitten biscuits.
With regard to the hog house, yes there are potentially other things which could be eating the food as well as hedgehogs. For instance, if it was cat food, many cats can get into hog houses and often additional measures need to be taken to deter them. But also rats or mice would go in if they smelt food.
Many people have trail cameras so that they can check who is entering hog houses or eating food.
It’s a good idea to leave water available for the hogs all day every day. Wide but shallow plant saucers are ideal for that – hogs are very clever at spilling water in smaller bowls!
Good luck. I hope it was hedgehogs eating the food!