I'm assuming you're talking about a live mouse? If so, you don't want to leave it in the tub with the snake. If the snake wanted to eat, it would have done so by now. If left alone, the mouse could chew on the snake.

Your options for dealing with an uneaten live rodent...

1. Take it out and set it up in its own enclosure with fresh food and water and try to feed it off the following week

2. See if the pet store you bought it from will accept it back again (some will accept them back in exchange for store credit...many will not)

3. Euthanize the rodent yourself and then either freeze it for a future feeding...or dispose of it