Once you are no longer with that employer, you don't have the option of paying the loan back. The remaining balance is considered a distribution to you.

Save the money, you'll need it next spring when the income tax and (probably) 10% early distribution penalties get added to your tax return.

I'm asking this because I still have before the end of the year to pay the loan. I also still have quite a bit in the 401K, so paying it back will increase its size too!

If indeed you have the ability to repay the loan, and you have the funds to do, i would strongly suggest you pay the loan, if you don't, you will lose all the future tax deferred earnings that would have accumulated into your 401k and when you retire, depending on your age and how your 401k does you could have a very comfortable retirement, or you could live on food stamps, the choice is yours, studies have shown, people when given the option of not paying back a 401k loan, never do, and don't realize THE mistake until they retire, PLEASE PLEASE, if possible pay it back!

22K is a significant balance and will go a long way toward keeping your retirement at the level it would be if you hadn't been laid off. Yes, I would definitely pay it back and avoid any penalties at all.