Arma 2 in HB Bundle removed game? Edit:Now reason is known.

If I try to go to the store page of ARMA 2 from my Steam profile it tries to go to steam id 33910 which does not exist. ARMA 2 is currently listed as 33900. Maybe steamdb can provide more info about the versions, but I don't have a lot of knowledge about game version info. I'm sure someone else will chime in soon.

https://steamdb.info/app/33900/
https://steamdb.info/app/33910/

Edit: I think you should be fine. I think this happens to everyone. I just checked a recent winner and their account is the same way. They won ARMA 2 that goes to the steam id 33900, but the game on their account tries to load steam id 33910. I checked their account on sgtools.info for broken rules and they have ARMA 2 whitelisted as a well know false positive which will not penalize the account.

I think you should be fine to mark it as received. If you have an issue, most other people would probably have the same issue and it would have to be fixed. I am not 100% positive, but i think this is correct.

https://www.steamgifts.com/go/comment/bWQabvu
https://www.steamgifts.com/go/comment/Upf02bJ
Write to SG support I think they aware about this issue.
In Steam client you can find this game, but not in web version.