Bug report: Dropped a crate into the water where the character is standing in the screenshot, it became invisible and can't be picked up again.
Possibly relevant info; while I threw the crate the egg was in the water, resting against the crate in the middle (took the screenshot after messing around for a while, seeing if I could solve the issue, that's why the egg isn't in the pic).
Edit: This might be the same bug already described by another commenter.