I feel your pain!!! I had a garter snake in my basement!(mind you I have 4 cats who sleep in the basement every night!! they were no help at all) I was told moth balls,lots of them, would to rid snakes. Well, we placed moth balls in the hole under floor (rooms added in the basement) where the snake was seen escaping to. Maybe just coincidence, or bad luck, the next morning I found the snake UPSTAIRS in my kitchen! (did I mention snakes REally creep me out?!) It was in front of an open sliding glass door looking out. Not sure if it came up stairs due to hunger, dislike of the moth ball scent or because it smelled fresh air. We kept still and watched it so it wouldn't disappear to another part of the house. I called a neighbor who came over, popped a box over the snake and dragged it outside on the rug the snake was on.
Thankfully I have seen no other snakes and I hope it stays that way! Good luck!