Two things,

1 In a few years, how would you like to look back on the situation
and think of yourself and your actions.

2 I had a similar thing happen and it was obvious when training the
new person I had the greater skills. Afterwards I found a job elsewhere. Two years later the place made a major restructuring, I
applied and got an even higher position, (I had since increased
my skill set at the new job). Things change and if their poor decisions caused you the loss of the promotion, things may right
themselves over time.