Hi Top Cat
It’s a bit of a ‘how long is a piece of string’ thing! There could be all sorts of reasons why the hogs disappeared, including finding somewhere else where they could find food and water. You say the habitat in your garden is good. Does that include a pond where the hogs could drink? But the dry weather might have made it difficult to find food, even in an otherwise good habitat – worms come to mind – they might have been staying well hidden underground.
If the hogs did find somewhere else where they were offered food and water, they may be back, but also may not return until after hibernation. Some males hibernate as early as September, so if they’ve found somewhere else they may not bother to come back this year, but I would expect them to explore the area again after hibernation. It’s unfortunate that you were away at that very hot, dry time, but hogs often ‘disappear’ for other reasons – for varying lengths of time. So they may be back.
I would continue doing what you are and offering food and water and hope they come back – you might just have to give them a bit of time, but hogs can be notoriously perverse.
Sorry I can’t be more positive, but fingers crossed they return. Good luck.