It could be that the battery did not get charged. Do you have the type of charger that tells you how much energy was put back into the battery? Or is it just a light that comes on? Do you have access to a voltmeter so you can measure the voltage of the battery? Voltmeters have really gotten cheap, by the way. You can get a decent one at Harbor Freight some times for $1.99 (plus shipping).

I'd try charging the battery again. How long did it take to charge after the flight? If it was less than 30 minutes, then it was probably not charged.