Tried looking in my search history too, to see what i search for around april may, only connection i found was to bitcoinincome, the scam site. So i think it's there the money has went
Not trying to cut your hopes here, but you have mentioned that the only connection you found is with a scam site. So if in case that the address belonged to them, you have no other option but to let the coins go, as it would be improbable for you to at least even talk to the owners of that site and ask them to return those coins to you. Also, I have a question, why wouldn't the withdrawal address change if you input them? Are there any kind of 'remember this certain address for future withdrawals' function in there?
I know, never really thought i would get the btc back, lost that hope when i start digging ;P X-value have the last withdraw adress in the window when you are going to do a withdraw! Why it didn't change I don't know, like I said it was the second time it happend.
Have you talked to them about this event? Why would the withdrawal window contain the same address when you last used it? That seems to be a bug on their system. If you have checked it first before you hit that withdraw button, you might as well saved that balance. Weird, if it is a system bug, say you changed the address on the box and yet the address didn't change, you can contact them about it as it will cause another problem in the future.