Can this get me pregnant?

My partner and I were having a sex marathon and taking off and putting on condoms fairly quickly. The next day (about 16 hours later) I went to the bathroom and felt something funny, and pulled an entire condom out of my vagina!!!!! I went to take plan B because I wasn't sure if that could have gotten me pregnant if there was sperm sitting there inside me? Also now rethinking about this... is it very likely that he didn't notice if he pulled out without the condom on??