I asked a question on this website approximately a week ago, and now it has dissapeared!?

If it had no answers, then the system would have automatically deleted it after one week, when this happens you don't get any notice sent to you. But if it was reported as a violation and deleted then you should have a violation notice from Yahoo in your inbox or spam folder, if you don't then you're fine, just ask your question again and perhaps place it in a different but related category.

If questions receive no answers a small computer program removes them in a week.

Yahoo deletes questions after 7 days if they haven't received an answer.

It was likely was auto deleted due to having no answers after 7 days.