All that sounds a little strange to me. Druids and Clerics have to memorize spells, but they always know all spells of a particular level. So your Druid should know all first-level Druid spells, even though you can only choose a couple to have ready.
Also that business of the spells changing/disappearing sounds very much like a bug.
I'd suggest starting a new game and creating a new Druid to see if the problem persists. If it does, you may want to go to the official IWD2 boards and check the tech support there for help.
The url is:
http://icewind2.blackisle.com/community.html
Nightowl2