Are you talking about a pinky mouse? If the bp is just under 2 feet long it will eat bigger prey than that. If you did not handle it during the first week of having it then you should be in good shape as long as husbandry is good. Petco feeds f/t, so it may have been intimidated by the live one. Try covering the enclosure with a towel or shirt to make it completely dark at feeding time. Good luck and keep us posted