The South Korean watched from the sidelines as the English champions defeated the London club after a penalty shootout.
After appearing in every minute of United's quarter and semi-final matches, it was expected that Park would play at least some part in Moscow.
"I was told that I wouldn't be playing just before the match," Park told South Korean television.
"After the manager announced the team he told me that he was sorry that he hadn't selected me." The 27 year-old was philosophical about the decision.
"The team won so I am happy. Personally it is frustrating not to play in such a big game but there will be other opportunities."