Happened to me already a few times during the event, and already a few time in the last year.
For doing the daily writs i'm taking food out of our guild bank, splitting it and putting it back in.
But it happened already a few times, that especially "Sipping Imga Tonic" and "Chicken Breast" didn't appear in the guild bank after putting it back in.
Neither is it shown in the guild log. So it must be lost on the way, diappearing into nowhere.
It's kinda annoying loosing stacks of food like this, even though theyre not that costy.