If you are lucky, one weighing is all you'll need. Place one ball on each opposing scale tray and if it tilts, you found the heavy ball. Then discard the other 25.
The puzzle does not specify being able to routinely perform this task.
Yeah, I know, you'll say it is implied.
Yeah, it's implied. But you're right; the riddle should state "what is the minimum number of weighings needed to guarantee a confirmation of which ball is the heavy one?".
It should also be stated that the other 26 balls weigh the same or the minimum number of weighings won't be the same as what the solution gives as an answer.