I'm on chapter 11, in Oerba village, and I just found Vanille's broken down pet robot thing. The game says I need to find 5 parts, but I can only find 3, and I've combed over the whole area a couple times now.
The 3 I did find appeared on the map as objects of interest, but no where on the map or in any buildings do their seem to be any more objects of interest.
 
 
Am I missing something, are some of them hidden or something?

I just put the game down about a half hour ago and that was the exact spot I stopped.  I haven't collected every piece yet but I do know that I picked up one from killing a Vampire at the bottom of the far side ramp.  Try finishing off some enemies if you had just been waltzing through them to get to the objective markers.

Hey there's one piece just into the next area of the town, if you follow your quest marker you'll find it. Also there's one on a vampire. 
 
This is really worth doing as you get little mini quest things to complete from the robot and he gives you insane items. Like I got 3 things that sold for 150k gil each and 2 things that give 160k+ exp when put onto a weapon with x3 multiplier which is insane!

Are there more of those robots?

...the last one is the monster, it's the one down the ramp by the trees.

where is the robot anyways? i cant seem to find it

Hey I found all of them.  I didn't know it was hard so I wasn't keeping track but I roughly recall where 4 are: 
 
1) From the windmill in the courtyard near the town entrance there's a bunch of little creatures running around, go up the small stairway to the engine room and fight the monster inside.  There's a bookshelf to examine with a battery component.  (Its the same monster as the one below the steps where the community kitchen is.)
 
2) The other hard one was randomly on the ground on the railroad tracks towards the end of town.  Keep examining stuff along the tracks and you'll find it. 
 
3) Power cables are found examining one of the carts. 
 
4) One of the monsters has one (as listed above) 
  
Hope that helps, though someone needs to confirm #2 and locate the 5th one.  Next time I play I'll keep better track. 
 
R/ 
Dnarturo