Sounds like you have a bit of a dilemma there, if you are going to be away and are not sure whether the hedgehog is hibernating in the garage. (They do sometimes wake up for short periods during hibernation). Hedgehogs are not best known for being easy to ‘lure out’. They pretty much have minds of their own. Is there anyone you could ask to keep putting the food out for it? I am assuming that it isn’t the sort of door you could make a hog sized small hole in?
Alternatively, maybe you could try to find it and relocate it. Do you have a shed which it could have access to? If you were going to try relocation you would need to have somewhere ready to put the hog in, for instance a wooden hedgehog box – a shoe box would be much too small. Also, a hog needs to weigh at least 450g to have a good chance of surviving hibernation. If it weighs less than that, you could try to contact a local carer (numbers normally available from BHPS – 01584 890801 although I don’t know how well that works during holiday times) it might be worth seeking their advice anyway – they would be aware of local weather conditions, etc.
If you try to relocate it, put on some gardening gloves or the like and carefully lift the hedgehog up and gently place it in the new place and preferably cover it with lots of leaves or similar, and leave lots more nearby – not sure the hog would take kindly to being shooed out with a brush! Keep providing it with food and water because, even if it is hibernating it may have been disturbed in the moving process and have ‘woken up’.
I would not normally recommend disturbing a sleeping or hibernating hedgehog at all, but, like you, wouldn’t want it to be shut in a garage with no food and water and no way out.
Good luck. I hope you manage to find a solution and the hedgehog safely survives the rest of the winter.