How big was the snake?
Were there any makings on the body?
Was it a solid color?
From the sound of what your daughter may have seen it was a non venomous snake that found its way in following after some food.There are very few venomous snakes in Missouri. Most like it is a stray and will get out the same way it got in. I am going to give a link to the non vemomous snakes in your area. Maybe your daughter can look at the pictures to identify it. I suspect this may be a black rat snake since it will chase after a mouse. Joan
http://mdc.mo.gov/nathis/herpetol/snake/snake1.htm This link has pictures to identify the snake.
This is the season that baies hatch and they are hungry and chasing food. To keep them away, you will need to clean leaf litter away and clear shrubbery away from the house. This should keep the food source away as well as the snakes since shrubbery and leaf litter is a great hiding place for the snake as well as their prey items.you will want to seal off any cracks or holes. You can try putting out some sticky traps to see if you can catch the snake, but I suspect it is gone by now. Joan
The types of Venomous snakes do not match the description that your daugher has given. Several are Rattle snakes, one is a water Moccasin and one is a Copperhead.Most likely this was a rat snake or garter snake from the size and description. Even small the Rattle snakes can be very aggressive. I am pretty sure your basement guest is on its way to find some prey in another area. Joan
I live in Fl, where we see a little of everything, so your dilema is an everyday question for me.I hope you will sleep easier tonight. Joan