It is always hard to face down rejection especially if you love your job and give everything to it.
I expect we have all been there, I know I have, but you do have to choose one of three option
Go back with bad grace, hate the “powers that be” who rejected you and continue to be miserable
Go back determined to show them what they are missing, enjoy the company of your work colleagues (who knows the person who got the job might be useless, if female go off on maternity leave or indeed be a nice person to work with
Go back, continue to do a good job and look out for the next vacancy which catches your eye.
You could of course also resign but that might be cutting off your nose to spite your face
or it might be a wake up call to those who took you for granted.
Whatever you choose, dress to kill, lippy on and make sure you tell everybody what a wonderful time you have had on leave.
(Got time to do a bit of fake tan?)
What is that quote about “not letting the buggers grind you down”?