Ouch!! That'll be why the footpump didn't put any air in!
A little off - road tip, don't tighten the valve nut down to the rim, use it as a locknut for the dustcap. That way you can see at a glance (pitstops etc!) if the tyre is "creeping" round the rim by the valve being at an angle, hopefully before it rips the valve off! And it gives a bit more flexibilty to the valve and thus time before that happens.