You must have had wrong putting meter showing. Has happened to most of us. Most likely 150ft or 300ft meter. Can happen by accident, here's an example. Bear with me here now, no butting in and no saying this didn't happen for you, these are just examples (real ones):
As well as clicking to do things, e.g. changing clubs, changing the meter on a putter, there are also keyboard shortcuts. Many times I've started typing into the chat box in a game only to be blinded by constantly changing camera angles! Don't know how or when it happens, but if something (don't know what) hasn't got 'focus', then the keyboard becomes your control tool. And when it has control, it changes things without you necessarily being aware.
Another example...
You have a mouse with a scroll wheel. if you hover over the club selected and scroll the wheel, the clubs change up or down. If the putter is selected and you hover over the putter max distance and scroll the wheel, the max distance changes up or down.
And one more...
You may have been just on the fringe, in which case it may well give you the 150ft meter. Obviously that is too much for a 15ft putt, but if you didn't notice it and didn't change it, you ball will go... well... a country mile!
Like I said, these are just examples of how it might have happened. So, just accept you made a mistake and move on to the next hole. You sure won't do it too often any more! It's just like hitting a 9-iron in real golf and finding that you've come up 30 yards short because you thought you picked out the 6-iron.