Lost iPhone containing important phone number what can I do?

I lost an iPhone a few weeks ago that contained a very important phone number of mine. Sadly I didn't back up my device and don't use iCloud. Would there be any way of retrieving that phone number? Or am I screwed?

If you have dialed or received a call using that number, check you cell phone service provider bill. It should be listed. If you don't have the bill, the billing history may be online with the cell phone service provider. If that number never called you or you never called that number, you're screwed.

You are effectively screwed unless you can get the phone back.