I hope Stitch is okay! It's so scary when a bird might be sick.
If it turns out that she already was sick when she was at Petco, she would be far from the only sick bird they've ever had. Just thought I might tell you that Petco has been in quite a bit of trouble lately for taking bad care of their animals, and even for many cases of cruelty. For example, one Petco employee actually PURPOSELY vacuumed up a parakeet and laughed about it with some other employees.
A LOT of their stores have gotten in trouble for this sort of stuff, and for neglecting their animals to the point of sickness and death, and then leaving these animals on display for customers to see. Anyway, I really hope Stitch is okay, but if she isn't, I wouldn't go back to that Petco if I were you in case they're one of the stores that has been in trouble. If you want, you can read about this stuff at www.petcocruelty.com.
I hope she's okay! Good luck!
Oh, and I hope I haven't offended anyone who is a loyal Petco customer! Just thought I'd share this, cuz it's pretty bad stuff.