2006 #13 Putter Used as Ball Marker

The Scene:
We were playing hole #18. All four balls lay on the green. I was away. I walked to my ball and placed my long putter behind it. Keeping my putter in place, I leaned over and lined up my ball. Then I removed my putter. But as I removed it, I twisted it against the ball and the ball rolled away a couple of inches. I replaced the ball. Should I take a penalty?

What would you do?

We weren’t sure what to do so we reasoned as follows:
First, I used my putter as a ball marker. Is that legal?
Yes, Decision 20-1/16 says
Examples of methods of marking the position of a ball which are not recommended, but are permissible, are as follows: 
• placing the toe of a club at the side of, or behind, the ball;

Second, when I removed my ‘ball marker’, the ball moved. Is there a penalty?
The following decision says there is no penalty.
20-3a/1 Ball Moved in Removing Ball-Marker After Replacing Ball
Q. A player replaces his ball under a Rule and, in the act of removing the object marking its position, accidentally moves the ball. What is the ruling? 
A. Removal of the ball-marker is part of the replacement process. Accordingly, under Rule 20-3a, no penalty is incurred, and the ball must be replaced.

Third, to make doubly sure, we phoned the pro shop. They checked it out and said that as long as I had replaced the ball there was no penalty.

REMEMBER: If you accidentally move your ball when you lift the ball marker, there is no penalty IF you replace the ball.