ghost in electrical

ok i posted a problem a few months back about problems with getting power from my battery to my fuse block, thought i had fixed it and it came back, now i'm totaly confused. i had just started my truck, drove about 10 ft and i lost all power. i checked continuity between the end of + batt cable and the fuse block, had continuity, pluged it back into my batt and checked voltage and i had none. i'm totaly confused. after playing around with it, i took the batt shelf out and there is a fuse below it. i dont know if there is a problem there, but after going through all the work of pulling it all out i decided to hook the cables back up to the batt for shits and giggles and it worked fine. i then cleaned up all the terminals and connections just for good messure and put it all back together. its still working fine, but i dont want this to happen at some random time when i'm away from any tools. if anyone has any ideas please let me know!
p.s. last week while driving around in the floods we were having here in mn, i stalled my truck out. it turned out water had just gotten into my intake and i needed to replace the filter. it works fine, and i dont think one had to do with the other, but it may be a piece of the puzzle

You could have a battery terminal problem. When you check your terminals for voltage how did you do it? Did you check directly from the battery negative terminal across to the positive terminal? i ask this becasue if you checked by grounding the probe anywhere other than the terminal, you could have a negative(ground) problem. Check your battery's termainls and then your wiring.

i checked it from the ground on the batt. i didn't check anywhere else because i took a jumper cable and went from the positive side and connected it right to the fuse block and everthing turned on and i was able to start the truck and move it. After driving it yesterday, i did notice that my truck is charging better than before. I replaced the alt about 3 months ago and i was getting a charge at 14V, and then recently i noticed it was only charging at around 12V. Now after i had this problem its charging at 14V again.

I've soaked the connectors at the end of the battery cables/battery end, in baking soda and water to clean corrosion.

i checked it from the ground on the batt. i didn't check anywhere else because i took a jumper cable and went from the positive side and connected it right to the fuse block and everthing turned on and i was able to start the truck and move it. After driving it yesterday, i did notice that my truck is charging better than before. I replaced the alt about 3 months ago and i was getting a charge at 14V, and then recently i noticed it was only charging at around 12V. Now after i had this problem its charging at 14V again.
classic grounding problem. by bypassing the grounding problem youre bypassing the problem. if your not getting 14v while running the engine youre running off the batt and running the batt down. a quick check to confirm a bad gound is to check for voltage on the coolant. take the rad cap off, engine cool, and start her up. use your digital volt meter to measure the voltage on the coolant by sticking the pos lead in the coolant and grounding the neg to a good body ground. anything more than .03 volts on the coolant is a problem.

i'm a little confused as to how it is a grounding problem. I think, and perhaps i am wrong, but if there was a grounding problem then when i jumped it from the positive side of the batt, directly to the fuse block, then to me it seems to be a problem on the positive side, not the ground. Like i said i could be off my rocker,