Yep when you buy and feed live you are going to have this happen so best as PK said to have a small rodent setup handy. If your snake doesn't eat this week then you've just got a nicer, fatter live prey item for next week. All you really need for such temporary housing is a good sturdy small plastic box with lots of holes melted in the lid (or a bit of the lid cut out and covered in strong wire mesh), a small water bottle, a dish for food and if you want toss in some toilet paper rolls or a small kleenex box for the mouse to goof around with (more to do, the less chewing the little fuzzy horrors do LOL). I have a spare 5 gallon tank that works perfectly for the occasional left over live mouse feeder.