What should I do?

Well my girlfriend has pretty stock parents I mean I haven't even been in her room. The thing is, I am 20 ans she is 19. We have been together for 10 months. We just started getting sexual. Today we got into it and I took off one condom I thought I put it in the trash next to my desk. I couldn't find it after so I said I would look for it. Well my girlfriend went home. Her mom tells her to get in the car as soon as she gets home. They rush off. Then when getting out of the car her mom grabs her purse and nothing else but that condom I couldn't find. Her mom ask her what is this? My girlfriend texted me this a few minutes ago. What should I do?