One is the line code indicating a number in the United States. If you look up international area codes on google, you can find out which it is. I think Germany is one of the ones that you would need thirteen numbers for.
Oh, also, most cell phones don't require the one at the front, so it could have been a standard number (area code, prefix, line) with keypad commands, such as voicemail. If it was local that would even take off the area code.
Or, the case could be (area code, prefix, line, extension).
I hope that helps and I hope it is really not anything serious.