The duck pond without ducks: should we assume the ducks were sucked into a crack? Or will this be explained more next season to?

Was this mentioned after TEH and I missed it, or have you been wondering about it all this time? I had pretty much assumed the duck pond thing was just a random philosophical question with no particular plot significance, although it would certainly be interesting if it came up again. Incidentally, I can totally imagine a bunch of psycholinguists writing papers about why it's called a duck pond when there are no ducks in it.