2011 Subaru Forester Check Engine Light

Have you retrieved the code? It may or may not be related to your gas cap. Take it to a parts shop, they'll read the code for free, you can google it or post it here if they don't know what it is. Not all "gas cap" DTCs are attributable to the gas cap, but some other component of the EVAP system.

Go to a local auto parts store and have them read the codes and reset them. Write the codes down just in case there is an issue. Post them here if necessary. This is usually a free service.

Get a nice cheap scanner as you'll use it often over the next years. Disconnecting the battery for a few hours may do the trick, btw, but often a scanner is needed to erase any CEL locked in memory. I like the baby ACTRON for $40, for example.

Thank you both for you answers and help! As I was pulling in to the shop unplanned on getting the code read at, the light turned off, so all's well that ends well!

The code will still be stored in the computer, with or without the check engine light being on. I'd still get it read. Most CELs clear after one cycle, which is running the engine up to temperature and then off. However some safety related codes won't turn off and some codes require more than one cycle to clear. That might have been your case with the loose gas cap.