Someone already suggested this issue. http://feedback.dayzgame.com/view.php?id=1592

Sometimes they will appear after a minute or two, sometimes they never will. I've also reported this issue: http://feedback.dayzgame.com/view.php?id=4735

This seems to happen more usually indoor. Try to do that outdoor next time. That's the only thing I can suggest until the bug's fixed.

Sometimes it will never appear. I got my cooking pot, gas stove and gas canister bugged once when I put them on the ground floor inside a 2-stories high orange house, and can never find them.