I killed my alternator in a similar way when the truck was less than a month old, at a HUMMER Happening no less.
There is a trick that may or may not work but worth a try. Make sure your battery is charged and get the truck running. With it running, spray brake cleaner in the vents on the front of the alternator. Have a fire extinguisher handy, but I've never had one catch on fire. The problem is that the muddy water gets inside the alternator and coats the brushes. It will keep working until the mud dries and kills the electrical contact. This is more of a trail fix but may get you down the road for a while.