What did thought do?

Can anyone tell me the origin/ meaning/ ending of the phrase "You know what thought did...."

Please help.

"You know what thought did? He didn't do anything - he just thought he did." A piece of nonsense which basically points out the futility of thinking that something has been done without actually going and assuring oneself that it has in fact been done. So for example, and bear in mind that I ma demonstrably no budding playwright:-

"The basement's flooded!" "But I thought I turned the faucet off..." "Well, you know what thought did."