It seems they removed users also after airdrop end(even with a confirmation id) automatically without notify them or asking for more details.
https://forum.decred.org/threads/airdrop-rundown.313/
However, in response to community concern, and as a show of good faith, the project has decided to conduct another (and final) sweep of the database to check its integrity and remove problematic entrants that are identified as fraudulent. The outcome of this may result in each successful participant receiving slightly more coins than stated - but no less than 258.93958076.
Most likely case in IP addresses (no one knows how many claimants were per your public IP) or just simply bad luck.
I'll wait before I buy/mine any of decred. Too many qestionmarks and no responds.
So,who registered from same office/university was automatically removed after confirmation?
They could make a check from tor ip(that's was fraudolent), not from same ip.