If theres one, theres bound to be others, just put a couple of traps out before you go to bed, and its more than likely there will be one in them in the morning, repeat for a few more nights and that should get rid of them, if you don’t there will be loads of them in a short while, no point in getting sentimental about them, we were initially when we heard them scurrying around in our loft and left it a while, ended up getting 14 of them, & they had nibbled away at loads of pipe insulation.