Googling

I note that this blog is the number two returned site if you google - Once is happenstance, twice is coincidence, and the third time is enemy action meaning - I am so happy...

See here and here. And in case you didn't know, the quotation is my favourite Ian Fleming line; it's from Goldfinger, in fact it's said by Auric Goldfinger himself

"Once is happenstance. Twice is coincidence. The third time it's enemy action."