“You wouldn't happen to know anyone who does, would you?”
You have an old Volkswagen car that has some engine trouble. You're looking for a mechanic to fix it. You call one auto repair shop, but they don't work on that kind of car, so you ask them this.
You wouldn't happen to know anyone who does, would you?
Use the phrase "happen to ___" to talk about something that doesn't seem very likely. One way this is useful is for asking questions, even though you don't think the listener will know the answer:
Do you happen to know a guy by the name of Fred Breedlove?
In this example, you ask "Do you happen to..." because you think that the listener probably doesn't know this person. You would ask this question if this person was from the same town as Fred, or went to the same large university as Fred, or worked at the same large company.
You can also use "happen to ___" to ask questions politely, even when you do think the listener's answer will be "yes":
Excuse me, would you happen to have a pen I could borrow?
"Have", "see", and "know" are the most common verbs that follow "happen to".
This is a very polite way of asking a question. Use it when the listener might not have an answer for you, or might not want to give an answer.
In the example above, you're asking the mechanic for the name of another mechanic who works on the kind of car you have. He might not know of a good answer, and even if he does know he might not want to tell you because the other mechanic is his competitor in a way. So it's good to ask in a polite way.
We use the word "anyone" in negative sentences and questions:
I don't know anyone who works on old Volkswagens.
Do you know anyone who works on old Volkswagens?
In positive sentences, use "someone":
Yeah, I know someone who works on Volkswagens over in New Jersey.
In the example at top, "who does" means "who works on Volkswagens". You can imagine that the conversation went something like this:
A: Hi, I have a problem with my '79 Volkswagen bus. Do you work on those?
B: No, I'm sorry, we don't.
A: Oh, OK. Thanks anyway. You wouldn't happen to know anyone who does, would you?