Travelling Frogs?

I've had numerous frogs take up residence in my small pond for a few weeks at a
time, and I've often wondered where they come from, and where do they go from
here? I found a rather large, striped one in the pond today, that wasn't there
last week. In fact, there have been no frogs in my pond for the last two
months. Earlier in the year, there have been from 1 to 3 frogs in my pond at
any given time, but they're not always the same frogs. It seems like my pond
is a frog motel, that they stay in during their travels. I never see frogs in
my yard or in the streets, (I live in a suburban area), the nearest body of
frog-friendly water is over 1/4 mile away, so I wonder how they travel to and
from my pond. Anyone else have this situation?
Regards,
Byron Wood