Does mid cycle spotting means ovulation has taken place. i spotted on day 12 of my cycle. did pelvic scan on day 15 and no egg seen?

Not necessarily: It's not uncommon to have some random spotting here and there during some cycles, due to short-term changes in your hormones which can be caused by stress and other environmental factors. If there was no egg seen then I wouldn't be so sure you ovulated at all. It's not particularly common to spot when you ovulate. Changes in cervical mucus are a better predictor of ovulation.