Well.... think of it this way; When a cell goes that bad it needs to release pressure and all its liquid guts come out with it when that pressure finds a hole. However, once it has found that hole it doesn't really need another one so the goop coming out of a cell more often than not will remain very very localised (and alkaline cells are constructed in such a way that this hole will be found at the negative pole 99% of the time). It is of course possible for this chemical stuff to work its way around the cell and up in to every nook and cranny you can think of, especially in tight locations like a flashlight, but that generally needs time. So as long as you didn't leave the leaky battery in the light for say a year or something its very possible that you are indeed looking at a very localised little chemical spill. In flashlights when you don't see any damage from a cell mishap like this you are pretty much fine. The green and salty white rock-like formations this process produces are very hard to miss.