I'm reading a book about construction grammar. There is an example sentence in the book: There was cat all over the road.
The book says this is a tragic story (a cat was dead), which makes me a little confused. Because according to my knowledge, the more acceptable sentence is "There were cats all over the road". However, this sentence has nothing to do with one pathetic cat.
So my questions are:
① Why does this sentence mean the cat was dead ?
② If it does have a special meaning, Is this a generally accepted expression or just a temporary art of speech? (Because this sentence would be considered grammatically incorrect in English learning.)
Thanks a lot!