Atamagaokashii
Newbie
Gmail has an option that saves addresses and info from people that email you if they were not in your contact list prior; could this have happened and your sister's phone sync'd and she saw it and called to see who it is?
Although; my initial reaction from what your describing is that it was a sync'd/linked facebook account that might have gotten deleted internet-side and her phone just hasn't followed suit. My Dad's primary cell phone number on my phone defaulted to what was listed on his facebook "ask." and I had the the same problems dialing it. "Unknown number" and then dropped call.
Long shots, but I tried
Although; my initial reaction from what your describing is that it was a sync'd/linked facebook account that might have gotten deleted internet-side and her phone just hasn't followed suit. My Dad's primary cell phone number on my phone defaulted to what was listed on his facebook "ask." and I had the the same problems dialing it. "Unknown number" and then dropped call.
Long shots, but I tried
She was already in my Contacts. It just added another "mobile" phone entry at some point.....