Think you may have a similar problem to me - found a rather long slug in my kitchen when I went for a drink of water in the middle of the night. Goodness knows how it got in, but they do leave silvery trails.
Yep, definitely slugs. Not easy to find as they'll be hiding in a dark crevise during the day. Look behind the cupboard uprights or in the corners or gapps in the room. Alternatively you'll have to do a night watch and catch them at it!
slugs. Take a look after dark (lights out) and you'll find them. Find out where they get in and fill the hole or crack with bath sealant. It could be an odd one that's come in on your shoes.
check out for slugs after it is dark. if you are sure it is slugs, you can create a trap for them using yeast plus honey or stale beer, so that they get attracted. you can then use salt water or soapy water to kill them. if you need to pick them up, use a pair of chopsticks for your own safety.