What exactly grounded out? The case? The typical test is to use a voltmeter and see if you are getting 12v+ to the small lead on the fender mounted solenoid when you turn the key. If not, you have to find out why.
As a side test, run a jumper cable from the + side of the battery to that small post on the fender mounted solenoid. You should hear a click and the starter should engage. If it doesn't, you got a bad solenoid or starter.
Back to the 12+ on the small lead. Two main reasons you wouldn't get power would be neutral safety switch (part of the digital transmission range sender) and the ignition switch itself. You don't mention if its an auto or standard, so I'm assuming auto until you say different. Try starting in neutral or jiggle the gear selector around while you have the key in the start position. If that helps, replace the dtrs, if not - the switch.
In the meantime, to get it started, you should be able to put the key in the run position and then jump to the small post on the solenoid to crank it.
2003 F-250 XLT Crew Cab 7.3L, Chrome BigTex Grille Guard, Quad pillar - 3 ISSPRO gauges (trans, pyro, boost) and DP-Tuner F6; Roush fuel pressure / temperature / oil pressure gauges, Ford Severe Duty AIS, 31 row 6.0 transmission cooler, ScanGauge II, Marinco mod, Walker BTM