Same reason the OP's husband made the Challenge without meeting the conditions: you got lucky the first time, but it was an anomaly. As ResQTekBill aptly says, if you call, they will "fix" yours too - and downgrade the misatkenly upgraded fare to the one you originally purchased, which is the norm for upgrades (yes, you normally keep the fare you purchased for the purpose of EQ points, even if you are upgraded.)