Incorrect vesting % shown on 401(k)benefit statements

[chris]

Does a participant have any chance at holding plan liable where benefit statements have reflected 100% vesting even though participant's vesting % is less? Vesting is 5 yr/ 20% year. Participant was employed only 2 years, but after termination of employment annual statements showed 100% vested. Participant requested distribution and got about 40% of the $$ shown on the benefit statements. Any recent cases? Will "detrimental reliance" be the issue? Participant basically only received less than what the statements led him to believe he had. Fund manager has said it was an error and they're sorry for the confusion.????