My sister has been recording episodes of the show for me on WGN but she said it's not on anymore, at least it wasn't on last night. Any idea what happened to it?

Comes on in a couple of hours and next on Friday (WGN).

http://www.tvguide.com/tvshows/corner-gas/195679

Scroll down past News for airtimes.

Corner Gas was preempted Monday night for a double showing of Independence Day. It was also preempted last night for The Honeymooners marathon. For now it's staying in the 1:30 AM time slot, but that won't last long. Starting Monday for two weeks Corner Gas will be airing at 1:30 AM and it will also be airing at 4:00 AM. Unfortunately starting Monday, January 19 Corner Gas will no longer be on the daily lineup. The only day it will be on is Monday late nights three back-to-back episodes from 4-5:30AM. Here's the blog article on WGN's January changes.
http://www.sitcomsonline.com/blog/2008/12/wgn-america-january-2009-changes.html

Corner Gas was preempted Monday night for a double showing of Independence Day. It was also preempted last night for The Honeymooners marathon. For now it's staying in the 1:30 AM time slot, but that won't last long. Starting Monday for two weeks Corner Gas will be airing at 1:30 AM and it will also be airing at 4:00 AM. Unfortunately starting Monday, January 19 Corner Gas will no longer be on the daily lineup. The only day it will be on is Monday late nights three back-to-back episodes from 4-5:30AM. Here's the blog article on WGN's January changes.
http://www.sitcomsonline.com/blog/2008/12/wgn-america-january-2009-changes.html
Yeah, it says that CG had too small an audience to keep it in the prime time schedule; what a shame that the USA couldnt appreciate the funniest show on TV :( Oh well, fortunately, it's still on here [In Canada].....until spring when CG will be gone forever, at the end of season 6 (Unless the plans for a feature film come to bear) Glad I have all the seasons on DVD!

Thanks for all the information.