I have received an email from EBay that it's been sold to someone else but I can't find out any more info.
That seems very odd unless you did something! I cannot see how that could happen unless you relisted. Certainly do not click on any links in case of a hack/scam.
If buyer does not pay within 4 days the thing to do is to cancel "did not pay" and give him a defect.
There is sometimes a provision for you to offer a second chance but you would [presumably] know that you had done so.
@kay17072010