Q: Song will not sync with ipod

I recently decided to add new music to my ipod touch (4th generation, fully up to date) and decided to download itunes yesterday (on a Dell PC, the itunes is the most recent one since I downloaded it yesterday). The only successful way that I found to add music to my ipod is by going over to "recently added", go over the album, right clicking,and then selecting "add to device" and bingo, the song is added. This went well up until one song would not show up on my ipod. I have been manually managing my music so the box all the way at the bottom of device is already checked off. I do not want to unclick that box because it will delete all the music that I have downloaded from cd's on my ipod since they are not in the itunes library. IS THERE A WAY TO FIX THIS?! I really, really, do not want to download my cd's over again just for one song but it is annoying the f*** out of me that the one song is not on there yet all the other songs that I purchased I can just right click and select. If anyone has any advice on how to get around this problem that would be greatly appreciated.