I can confirm this bug.

I have gone into more detail about it here: http://feedback.dayzgame.com/view.php?id=19360

It happens with the Gas Canister as well as a second weapon.

If you want to actually drop the Gas Canister, you must drag it out of your inventory (after you attempt to drop it and it appears there). It is located at the top near your hat, gloves, and shoes.

I have reproduced this issue. It does not persist between character deaths (but I have not tried logging out and back in on a bugged character).