ummmmmmmmmm u cant get/catch the starter Pokemon back. u just have to trade with someone who does have the starter Pokemon. I think theres a way u can get a piplup egg from the daycare people but im not sure how. Srry to dissapoint :]
no
The starter pokemon for Diamond and Pearl are Turtwig, Piplup, and Chimchar.
Trade with another Pearl or Diamond.
There is no other way.
Chimchar
Choose it as your Starter Pokemon.
You have to choose it as a starter
piplup
you can get it as your starter Pokemon
I'm pretty sure that the only way to get another starter Pokemon in Pokemon diamond is to go to the Global Trade Station (GTS) and trade with someone.
Turtwig in Pokemon Pearl and Diamond.
you get piplup as a starter in Pokemon diamond/pearl/platinum