I could not pack it all up and take it with me, so I had to leave some items stashed on the woods during the update on two separate servers. After the update, four backpacks (some empty, some with items) left on the first server disappeared; two backpacks left on the second server were still there, although a few items disappeared from within the backpacks: an MP5, drum magazine, and 2-3 inconsequential items.

I did not expect any of the backpacks to survive, so I can't complain - just trying to make sense of how the world works in Chernarus.