Hi spo. It looks as though you've got a few questions in here, which makes answering your post a little more complicated.
First, to get vinegar, you need acetobacter (a type of bacteria), which is usually not found in clean wineries.
How can you tell a wine is cooked? It may smell of nuts or sherry or stewed fruit instead of having the vibrant fruit flavors that it's supposed to have. A slightly cooked wine may have dull aromas and flavors. Another clue for cooked wines: the cork might be pushed up a bit and there might be some wine dribble coming from under the foil (because the volume of wine increases when it's heated).
A single spike of heat can break the seal on the cork and expose your wine to oxygen. If this happens, I advise drinking the bottle ASAP. Seasonal fluctuations that don't get too hot or too cold are okay; the wines in my basement are still holding up okay. You do have to worry about more frequent fluctuations.
Extended exposure to warm temperatures will speed up the aging process. This is not a good thing. You can't rush mother nature; the wine doesn't really gain in complexity; instead, it simply gets tired and old before it's time.
Shipping wine in refigerated containers is expensive. Sometimes wines are exposed to heat en route and a few are damaged. I don't know about numbers, but I can say that in a couple decades of tasting wines from all over the world, I haven't encountered enough cooked wines to worry about shipping conditions.
Hope that helps.