This Seeking Tech guide will explain how you can find the two hidden puzzle pieces on the Crash Site stage. These aren’t mapped on the map and won’t appear until you meet some requirements.
For the first piece, you need to get the Heavy Roller prize item from the Gatcha Lab. Afterwards, head behind the controller ship on the Crash Site to find a makeshift bowling alley. You need to punch the bowling ball to knock down all the pins in order to get the puzzle to appear.
For the second piece, you need to get the Squawky prize item from the Gatcha Lab. You should then find the birds flying around with the puzzle piece on the outer edges of the Crash Site. You will need to jump from higher ground to grab it.