You should have a support issue open in your AWS portal now, if you need any help getting new keys for other apps. If you can't find it hit us up at support@mongohq.com and we'll escalate.
As a company we are now trying to figure out how long our access tokens have been out in the wild.
You should look into using separate AWS keys for your DB backups and whatever it is your app uses those credentials for. This not only prevents any future availability issues because of key revocation, it also allows you to set fine grained permissions on your access keys limited just to what they're being used for.