That's very sad. The mental image and the suffering the poor little guy must have gone through.
A while back someone posted a thread where a frog had ingested several rocks and they uploaded an X-ray image. Perhaps we should bump it if we can find it.
That is precisely why I brought my pacs home from the pet store they came from...they were housed on wet gravel. I did also speak to them about the issue.
I am sorry for your loss.