Lost 'phone

Whilst at the Bard on Sunday afternoon, a lady started wandering around waving a mobile phone " Anyone lost one?"
As she seemed somewhat lost herself, I took the phone off her and phoned O2 - the network provider in this case. Luckily, the mobile's number was written on the back. They couldn't help - it was against company policy to give out the names of mobile owners - even though I was phoning from the number concerned.
So I started to phone the people in the stored numbers. I asked if they recognised the number. The first two said they didn't and had no idea who it could be.
The third said: " Oh my God! What's happened?" When I calmed him down I told him it was a lost mobile, and, from his reaction, I assumed he knew who it was.
" Hang on hang on!" he shreeked," I'll need to read the number again!" There was a pause, followed by some muttering.
" Er ..actually I have no idea whose number it is" - end of conversation.
So I went into previously dialled numbers and dialled the first one. Fortunately, my enquiry was met with a calm man's voice, who opined it was his mother's number, her name was Mrs.X, and she was at the do with a Mrs.Y.
It transpired Mrs.X had gone home, but Mrs.Y was still there and promised to return the phone to her.
However, the non-recognition of the numbers set me thinking. It was a pretty old 'phone, with odd bits of cellotape on it. My eventual conclusion was that whoever had owned the phone before had stored numbers in it, but that Mrs. X had never deleted them. The old phone owner would have given his mates his new number, so they wouldn't recognise the old one on their screens.
I could have spent all afternoon contacting the stored numbers to no effect.