Minecraft directory doesn't have a 'Resource Packs' folder?
Solution 1:
If you rename the .minecraft folder temporarily to say, .minecraft-old, then run the game, this will force it to redownload everything. Then, start a new (temporary) world, and exit. This should recreate the missing folder.
After you've done this, you can copy your old worlds from the .minecraft-old directory into the new .minecraft directory.