One of the flags accidentally fell into the pot with the rejected ones!
Can you recover the lost flag?
Based on the hint of "23" I tried the obvious choice and submitted the 23rd flag, but it wasn't accepted. I then tried every flag with a "23" in the the line number, 123,223,230-239, 323 and 423, but again non were accepted.
I re-read the challenge and focused on the title choice of "Lost" along with the hint of "23". I wondered if this was a reference to the TV Show Lost. Throughout the series there was a reoccurring series of numbers, 4, 8, 15, 16, 23, 42.
23 represented Jack Shephard so I searched for a key that contained the string jack or j4ck but found none.
The accepted flag was, ``