Running the Nightfall with my buddy last night, on 3 characters. Complete first one and switch characters to do it again. My friend (if you check out my latest games you will see her gamertag) used the Destiny App to transfer items to the vault then onto her character. Get to the bit where it's best to use a sniper rifle (Blackhammer).......not on her character. No problem thought she, I'll just transfer it, thinking she had left it on another character. But no, not any, nor in the vault. Gone! Having Googled this issue it does not appear unique and whilst we'll run Crota a few times to see if we can get her another, it is a bit of a pain to think that something that took many hours to accrue, is lost through no fault of her own (and yes, it was locked!). So, a little cautionary advice; use the app at your own risk!