Server fault, is the reason behind this. See my comments elsewhere about the datacore blocking. What happens is, you connect when the server's data pipeline is blocked, and the game gives up and assumes you are a 'new blood' into the game. It then creates you a blank template character in Arma 3 default gear.
Bloody annoying, I know, but not a lot I can do about it until I find the root cause - which is akin to a needle in a haystack currently.
If you let me know how much you think you'll need to cover your losses, I'll happily refund you - but you will have a bit of a shopping trip on your hands (my apologies). Please, if possible, fill out the appropriate form - not because I'm a jobsworth, but because it gives me all the player-ID data and other stuff I need to be able to zero in on your record quickly, rather than faffing around through the database looking for the RIGHT HDGamer (there is more than one).
Cheers.
(Not responding to the BS about the MK18 here, because I've covered that elsewhere. If people have lost gear, start your own threads, please - don't join someone else's and complain about your own things. You won't get it any faster as a result (and you might even hinder the original plaintiff from getting their stuff quickly). Thanks.