How many years can a cat go missing?

In 2009 Sophie left home in Morley West Yorkshire, UK. She was being cared for by a relative of owner Craig Hurst. Perhaps it was the new circumstance of her life, or the loss, albeit, temporarily of owner Craig but she left disappearing  into the West Yorkshire hinterland. Recently in 2014 she turned up three miles away and was identified by the microchip and re-united with Craig. The lesson is always microchip!