Can't find my Samsung S3 phone

So this is the situation: three days ago I was looking for my Galaxy S3 and couldn't find it. It's an extra phone, so don't use it much. So I asked device manager, and it reported it online several days ago, but gave me a location at my address. I sent a ring signal but nowhere was any sound to be heard. The app said "ringing" so it must have communicated with the phone. Since then it reported my phone unavailable and available intermittently. I have called the phone and it rings silently before switching to the answering machine, so I conclude, that it's on and probably in a charger somewhere. It doesn't run several days without charge, I figure. Checking all outlets in the house and outside, I can't find a charger plugged in. I even checked my Google play to see if there might be installed some kind of GPS faker. No there isn't. Also... six days ago my location history reported the phone to be travelling by train 120 miles away and being there for almost a day before suddenly returning back to my house. I'm puzzled, to say the least. Are there any tools to help me? Or what might be going on?