iPod touch 6 not showing all albums?
This may or may not help you, but I actually had the same problem.  Which lead me to this page because I did a Google search.

I had an artist with 11 albums in iTunes.  But on my iPod it only showed 10 albums.  However, when I searched for specific tracks on the "missing" album they would show up and play fine.

I messed around with iTunes a little and followed the other answer's suggestion.  I selected the album in artists view, right clicked on the album art (this will open up the properties for the entire album, not for a specific song.  You can also make changes and apply them to the entire album rather than having to go song by song).

At the bottom of the window there is a box "Album is a compilation of songs by various artists."  Somehow, that was checked.  Which is odd because way back when I started ripping my CDs to iTunes I would let iTunes download the information for the CDs from their database.  Anyway, I unchecked that, synced the iPod again, and the 11th album showed up under the artist.