My guppies disappeared without a trace?

I just came back from a 1 week trip out of state. Before I left, I bought 4 neon tetra, and 4 guppies, along with 1 goldfish that is not quiet big that I've had for awhile before that. I've set up a new aquarium for them all, and they all seemed pretty well adapted to the environment before I left. Then I left for exactly 1 week and 1 day, so you can say all the fishes was starving or went without food for that long of a time. But for some reason, when I came back, I only saw my 4 neon tetras, the 1 (fantail) goldfish, but ONLY 1 guppy left. I have no idea where the other 3 guppies dissapeared too. I didn't see any dead or floating fish, plus my aquarium is pretty much covered with the lid so I dont think the fish can jump anywhere. Would the goldfish probably gobbled it up? It's body seemed pretty normal.. It's 3 guppies, it wouldn't be able to be eaten by the goldfish within 1 week without the goldfish showing any signs? Anyone have any idea? Please help because I'm still very confused lol..