I would first confirm if this is an hours requirement vs elapsed time method for service and vesting and is your vesting schedule cliff or graded?
If said participant worked 1000+ hours in the Plan year for 2014, 2017, that is for sure 2 years of service.
Depending on other items, did the participant take a distribution? This will likely impact if they have a match or profit sharing contributions. They might have forfeited funds and if are fully vested, might not be showing depending on the Plan setup.