Hello, CALADOR. Welcome, and salutations! I'm not too certain about it, but because you found it at PETCO, I'm thinking maybe a American Bullfrog? The color looks a little off, but I haven't seen too many freshly metamorphosed American Bullfrogs before. There's some members here that should be able to tell you what kind of frog you have, and I'm only making a guess. I observe toads mainly, so I usually fail at IDing Ranid Frogs. I'm thinking Am. Bullfrog, though. They are sold alot at petstores, and as fish bait at bait shops. Nice looking froglet, though. Good luck!