Baby Yoshi respawn times?

I just broke out my new "Super Luigi U" standalone game, and began playing from the beginning. I soon encounter a little creature claiming to be a Baby Yoshi (directly after the first mini-castle if I'm not mistaken), who begins following me around and going into levels with me.

I only played one level with him (Piranha Heights) when I die and he disappears. But when I went back to the spot where I originally met him, he wasn't there either! After a quick Google search I found people saying the young Yoshi's do spawn back, but that it just "happens".

So my question is: How long is it until Baby Yoshi's will come back? What is the criteria?

Well in my time playing the game I ended up figuring it out myself! They respawn every time you win a level, that's it. (Losing the level doesn't count, though. Try it.)