One week.
That's how long it will take to train your frog. Once you "tame" it, you will be able to ID it.
Every time you approach your pond, bring a worm and throw it (as best you can) to the frog location. After a couple of days, it will associate you with food. After a couple more days, it wont run away. After a couple more days, it will wait for you.
Pretty soon after that, you'll be able to pick it up.
This works. If I so much as bring a shovel and start digging anywhere by my pond, the frogs all line up and wait. They know I'm the food lady.
The down side, of course, is that I must be VERY careful with that shovel.
Try it! It's fun to fool with frogs.
All the neighborhood kids bring me frogs and toads... they think (automatically) that they belong in a pond. It's cute!