Tadpoles take a long time to metamorphisize. Bullfrogs can take 2 years. My Gulf Coast Toad 'poles take just about all summer, before they develop legs and hop off. And that's with me feeding them and pampering them. In a puddle in the street with nothing to eat, it must take even longer to transform.
I had a job in Anuhuac once, and they had tons of green tree frogs - of which I have none here 60 miles west in Houston. After work, I would get a net and a jar and go grabbing them off the windows of the house, where they stuck themselves so as to catch the bugs that flew toward the light.
No matter how many I transported back home, after a night or two, I never heard them again. :'(