Attention Span

Today was a pretty nice sunny day so I decided to wash a few of the windows. Bob was helping me move the ladder from window to window and basically just "holding" the ladder.
About halfway through I asked if he would go in and get me a few paper towels.
"You Bet", He said-- "I'll be right back"  He said--

He didnt come back..Up on the ladder I was straining to see through the window what he might be doing in the house. Ah-- There he was- sitting in his armchair watching TV.
I knocked on the window to get his attention- he got up and went to the front door to see who was there. He opened it- Looked around, didnt see anyone so he closed it and went back to his chair. I knocked on the window again- - the same thing- He went to the front door again.
I knocked again- this time really  LOUD.. BOB-  OVER HERE--


He comes to the window- opens it and says--
 "what are you doing/"
Me-"Washing windows"
Him- "you should have asked me for help"
Me- "maybe next time"
Him- "Someone is playing jokes- they knocked on the door and then ran off or something"
Me- "Dont worry- I'll keep a lookout for them. Can You hand me a few paper towels?"