No it happens. At least you have a "right" to be doing the act. My grandson at the age of 14 caught his mother, my daughter, naked on the couch with another woman while his father was at work one day. That is in another category entirely.
In just a few weeks time she will forget about the whole thing. That's the wonderful thing about small children. They rarely remember anything during there time's as a child. Give it a little while and you'll see. Hope this helped. :)
She should be alright I walked in on my parents before when I were about her age or three. And she at that age should be fine because she's too little to have even knew what business you two were doing of making the bed rock. Just next time make sure she's asleep or away at grandparents house and keep your freaking bedroom door locked....
Don't worry! She's but a baby, she won't understand. If she asks just say that momma and daddy are spending each others special time together. Tell her its night night time and sing her to sleep in her own room. Make sure she has a favorite toy, and next time shut the door farther-teach her what that means and you can still have love. It doesn't ruin anything. Have fun.