I don't know about a high percentage, but there is a chance. I'd suggest the morning after pill, but after 2 days.... might not be effective.
I've never had a condom "lost" inside me, but once it was left behind, sort of half in/half out. My reaction was "Hey you left something behind!"
I'm sure you'll be fine though. The switching positions thing can get a bit tricky... condoms tend to like slipping off...