I'm really worried for my friend?!!!!?

Me and my four best friends were at a sleep over at my friend's barn a few days ago. We were all having fun, maybe a little to much.. We crashed around three, and about 2 hours later I woke up. It was pitch black and I started getting really scared. I found my flashlight and shined it around to see who else was awake, but that's when I saw that Allison was gone. She had left all her stuff and she would never leave without taking her phone with her! I walked outside and looked around for her, I was walking closer to her house when I think I heard her scream.. I ran back to the barn and woke up the other girls. That was two days ago and she is still gone. What should we do? We're desperate and hopeless, and we don't see a way out of this. None of us remember anything about that night.. Please, help us.