Yesterday, I unholstered my M&P 9c (10 rd mag), and released the magazine to go safe before I went to clean the pistol. After cleaning, I looked on the floor and there was round lying there from when I removed the mag. I've never seen this happen before (and no, I didn't have a chambered round when I pulled the slide back). Anyone know what may have caused this and does it suggest a problem with the mag or the action? Thanks.