Ladies/Men: Has this ever happened to you ?

Well my girlfriend got very upset because after our intimate time together while just resting and laying in bed, she found the condom at the bottom of her feet. Yes, it fell out, I don't know when it fell out, but I'm thinking it was in the middle of the whole session. Now she's blaming me claiming I did it on purpose. Why would I do that, I do not want to have any more babies..! Has this happened to anyone else ?