If you're slotting an ornithologist doff mission and for whatever reason exit the doff mission window, the mission has already gone on cooldown for 24 hours, even though you haven't actually *launched it*. Which means you can't go back into the menu and put the doffs in and do it if you leave the window for any reason.
Related to this: The PRESS F FOR INTERACT bar in the middle of your screen for the Ornithologist will randomly set focus and overlay all your other menus, and it appears RIGHT IN THE MIDDLE WHERE MY DOFFS ARE, so it's incredibly easy to misclick. And if you misclick, what happens? Your doff window closes.
If the mission you just selected and accidentally closed is no longer on the ornithologist's list ( like' raise hatchling from egg' ), I've always found it is still available on my Character's DOFF assignment list under "Personal".