Am I missing something? Or are / were you just being cheap?
Couldn't you have had someone FedEx, DHL, or UPS the keys to you at your hotel overseas?
I mean, if we are talking a single key, it could go at the letter rate.
And I assumed you are on at least a week-long trip? So even if you could get 4 day service to India, so be it.
Also, beyond the Continental lost & found form, try contacting any and all airports you transited through on your way. You may have taken your keys out at security, and left them there, or they could have fallen out in the terminal.