Disappeared hogs

I have had hedgehogs in my garden for about 18 months I leave food out for them every night, My question is the food has not been touched for 3 nights now and I'm a bit concerned to what may have happened to them?

There is a purpose built house in the garden which I checked they have made a nest in there but no sign of them.

Over the time I have seen 3 at one time so they are quite popular where I live.

I would appreciate any help, Thank you