I'm not sure if maybe I just missed this feature but it would be really useful to be able to sort by collector number.
Thanks for the feedback.
At this time, the database does not include collector's number information. Many requests have come in to add the collector's number (I've submitted one of them :D ), since it would help with entering foreign cards when you don't know the English name.
Sebi and the crew are aware of the requests. Currently they are working to get out a redesign of the trade interface, along with some other fixes from the January release. While oft requested, there's no word as to if it will be incorporated any time soon.
Sebi and crew aren't getting a paycheck for developing and maintaining the site, so we all (the community) appreciate the work they do put in and understand that they have lives apart from this site.