My Kingdom for a Tadpole!

It is inherent in human existence that we can never know the answers to all of life's mysteries.  The very fact of our presence here on Earth is the greatest conundrum of them all.
And so the question that has been taxing my brain these past few months and which has remained unsolved, must now be aired in public.  It is this;
What has happened to all the frog spawn?
Admittedly, the breeding cycle of amphibians is not normally uppermost in my mind (except, obviously, on Thursdays) and to be fair I don't suppose that frogs are overly concerned with human procreational habits either (not even on Thursdays).
However, having installed a small pond in my garden a year or so ago, which is now established with a second season of healthy-looking plants, I wanted to introduce some wildlife to supplement the one beetle, one pond skater and ten dead and bloated worms that had found their own way into what is obviously a less than attractive natural habitat.
The Expedition started in early March in a casual manner; whenever I happened to be near a body of still water larger than a puddle, I had a quick look for the telltale mass of speckled jelly.
Later I started to make special trips to local and not so local ponds, clutching a suitable container for the transport of the precious cargo, while at the same time trying not to look like a nine year old schoolboy. (Actually that bit is quite easy!) But every location was characterised by a distinct absence of amphibious activity. Nothing but beetles and dead worms, and I had an adequate supply of both of those.
If you believe the wild life programmes on television, the forests and moorlands flourish with all manner of animals and insects, while the ponds and lochs are home to tsunami-inducing quantities of life actively reproducing at prodigious rates.
To which I reply with the only phrase in the English language in which two positives make a negative.
"Yeah, right!"
I must now await a Biblical plague of frogs to descend on my garden.